@sheikah i think in my case it only my dns problem, earlier i using custom dns ip address, for working in my client's vpn network, and forgot abort changes after complete.
I suggest, that problem "can not resolved api.faforever.com", may be resolved by changing user's network settings for using dns from CloudFlare or Google.

CloudFlare DNS
dns1_ip_v4: 1.1.1.1
dns2_ip_v4: 1.0.0.1

Google DNS
dns1_ip_v4: 8.8.8.8
dns2_ip_v4: 8.8.4.4

Additional: it can increase connection quality in game and decrease ping.

@sheikah thank you, changed network's dns to auto, resolved my problem with:

sure:java.util.concurrent.CompletionException: org.springframework.web.reactive.function.client.WebClientRequestException: failed to resolve 'api.faforever.com'; nested exception is java.net.UnknownHostException: failed to resolve 'api.faforever.com'