I too have installed some flatpak apps this week with no problem but just tried a random app now for the halibut:
"tls handshake" in forum search was interesting: there was a flatpak related post that was solved by a system update (sudo eopkg up). If you are up to date then I have no other suggestions.
Gut instinct, however, believes it's on their end; try again tomorrow...(?)
2 cents
