Hello I have this error too.
I have reinstalled the launcher on my system drive and it has not solved the problem.

Thank you

java.lang.IllegalStateException: No endpoint has been specified
at com.faforever.client.login.OAuthValuesReceiver.lambda$getRedirectUris$1(OAuthValuesReceiver.java:77)
at java.base/java.util.Optional.orElseThrow(Optional.java:403)
at com.faforever.client.login.OAuthValuesReceiver.getRedirectUris(OAuthValuesReceiver.java:77)
at com.faforever.client.login.OAuthValuesReceiver.lambda$receiveValues$0(OAuthValuesReceiver.java:54)
at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1768)
at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1760)
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373)
at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182)
at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655)
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622)
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165)