Managed to sort this issue out although no idea why this was happening. The issue seemed to be in downloading the nx2 files. It would get part way through downloading one and then throw up the error, To fix this I launched a vpn, pointed at my own country, and it was able to download the files fine and launch the co-op with no errors.

I generally have no connection problems watching youtube/netflix/using discord ect so why I needed a vpn to stay connected to download files I have no idea.

So if anyone else gets this tag mismatch error, try using a vpn or mobile hotspot I guess.

Managed to sort this issue out although no idea why this was happening. The issue seemed to be in downloading the nx2 files. It would get part way through downloading one and then throw up the error, To fix this I launched a vpn, pointed at my own country, and it was able to download the files fine and launch the co-op with no errors.

I generally have no connection problems watching youtube/netflix/using discord ect so why I needed a vpn to stay connected to download files I have no idea.

So if anyone else gets this tag mismatch error, try using a vpn or mobile hotspot I guess.

Hi, I recently installed faf and linked my steam, I tried to host the Black day mission in the co-op and I always get the following error, then it loads up a lobby but I dont see any way of selecting a mission just skirmish maps. I dont have and never have had any mods installed in my forged alliance thus far.
Any ideas?

java.util.concurrent.CompletionException: java.lang.RuntimeException: javax.net.ssl.SSLException: Tag mismatch!
at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:331)
at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:346)
at java.base/java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:704)
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
at java.base/java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:2152)
at com.faforever.client.task.CompletableTask.lambda$new$1(CompletableTask.java:18)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.concurrent.EventHelper.fireEvent(EventHelper.java:219)
at javafx.concurrent.Task.fireEvent(Task.java:1358)
at javafx.concurrent.Task.setState(Task.java:709)
at javafx.concurrent.Task$TaskCallable.lambda$call$2(Task.java:1455)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:832)
Caused by: java.lang.RuntimeException: javax.net.ssl.SSLException: Tag mismatch!
at com.faforever.client.patch.SimpleHttpFeaturedModUpdaterTask.lambda$call$0(SimpleHttpFeaturedModUpdaterTask.java:80)
at java.base/java.lang.Iterable.forEach(Iterable.java:75)
at com.faforever.client.patch.SimpleHttpFeaturedModUpdaterTask.call(SimpleHttpFeaturedModUpdaterTask.java:64)
at com.faforever.client.patch.SimpleHttpFeaturedModUpdaterTask.call(SimpleHttpFeaturedModUpdaterTask.java:24)
at javafx.concurrent.Task$TaskCallable.call(Task.java:1425)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
... 1 more
Caused by: javax.net.ssl.SSLException: Tag mismatch!
at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:133)
at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:369)
at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:312)
at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:307)
at java.base/sun.security.ssl.SSLTransport.decode(SSLTransport.java:122)
at java.base/sun.security.ssl.SSLSocketImpl.decode(SSLSocketImpl.java:1491)
at java.base/sun.security.ssl.SSLSocketImpl.readApplicationRecord(SSLSocketImpl.java:1456)
at java.base/sun.security.ssl.SSLSocketImpl$AppInputStream.read(SSLSocketImpl.java:1038)
at java.base/java.io.BufferedInputStream.fill(BufferedInputStream.java:244)
at java.base/java.io.BufferedInputStream.read1(BufferedInputStream.java:284)
at java.base/java.io.BufferedInputStream.read(BufferedInputStream.java:343)
at java.base/sun.net.www.MeteredStream.read(MeteredStream.java:134)
at java.base/java.io.FilterInputStream.read(FilterInputStream.java:132)
at java.base/sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(HttpURLConnection.java:3540)
at java.base/sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(HttpURLConnection.java:3533)
at com.faforever.commons.io.ByteCopier.copy(ByteCopier.java:65)
at com.faforever.client.io.DownloadService.downloadFile(DownloadService.java:37)
at com.faforever.client.patch.SimpleHttpFeaturedModUpdaterTask.downloadFeaturedModFile(SimpleHttpFeaturedModUpdaterTask.java:112)
at com.faforever.client.patch.SimpleHttpFeaturedModUpdaterTask.lambda$call$0(SimpleHttpFeaturedModUpdaterTask.java:75)
... 8 more
Caused by: javax.crypto.AEADBadTagException: Tag mismatch!
at java.base/com.sun.crypto.provider.GaloisCounterMode.decryptFinal(GaloisCounterMode.java:621)
at java.base/com.sun.crypto.provider.CipherCore.finalNoPadding(CipherCore.java:1118)
at java.base/com.sun.crypto.provider.CipherCore.fillOutputBuffer(CipherCore.java:1055)
at java.base/com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:943)
at java.base/com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:491)
at java.base/javax.crypto.CipherSpi.bufferCrypt(CipherSpi.java:794)
at java.base/javax.crypto.CipherSpi.engineDoFinal(CipherSpi.java:730)
at java.base/javax.crypto.Cipher.doFinal(Cipher.java:2500)
at java.base/sun.security.ssl.SSLCipher$T13GcmReadCipherGenerator$GcmReadCipher.decrypt(SSLCipher.java:1930)
at java.base/sun.security.ssl.SSLSocketInputRecord.decodeInputRecord(SSLSocketInputRecord.java:260)
at java.base/sun.security.ssl.SSLSocketInputRecord.decode(SSLSocketInputRecord.java:181)
at java.base/sun.security.ssl.SSLTransport.decode(SSLTransport.java:110)
... 22 more