Might be worth sending a ticket to support if you haven’t already yet, with your guild and invite codes for ease of lookup for them.
Out of curiosity, are you still generating Seals as normal? and Event Points?
And maybe check whether any cards you get on PC show up in Mobile and vice versa, and whether troop/levels or trait increases change over as well.
One solution I can think of is to try uninstalling it from your Mobile device, see if your PC works normally then. And if so maybe try redownloading and re-linking the accounts.
Also worth noting that there was a new version that went out on Steam on Friday, so if for some reason Mobile and Steam are on different versions that might be causing issues.
Source on version stuff: