If you don’t know what a VPN is, you probably don’t have one installed. You’d be seeing VPN shown in the display, if you did.
Meta is suggesting a factory reset and starting over. If you want to do that, that’s your decision.
Alternatively, if a third-party app is not working for you, delete it and use something else. Delete WhatsApp, and use Apple Messages, Signal, or one of the many fine alternatives.
As for why they might be having issues with this app, Meta have published their “architecture”, and by all appearances, it’s massive, and seemingly unnecessarily and inordinately complex. Requiring an entire day to build an app is… unusual. So is wrapping…everything. And if something goes wrong somewhere in all that, well, here we are. As for other Meta app bugs, display scrolling was blowing up for Meta apps a week or three back, and they eventually fixed that in app updates.