I recently updated my apple iOS and now no longer have any of my offline favorites and see no way to even store favorites offline on my iPad Air

After hrs of troubleshooting with apple support it seems the problem must be with compatibility issues on UG's end. Be great if I can get a reply from UG support as this already negatively effected my last performance venue
Mine seems to be the same issue as yours however, its only after i not only updated my iPad but also synced it to iCloud (i think). Because at first i thought it was an apple problem, so i was on the phone to them for about 2 hours this morning, they even had me completely delete the app, and pay for it again at $27.99 (which is the pro version, and they are going to reimburse me for it). yet still none of which worked.
BUT! once i reinstalled the app (and whilst connected to wifi, all my tabs downloaded again, which tells me it has something to do with iCloud)
I feel your pain, for I'm really upset also, what was a great app, has no major issues.