I am having the same issue on xbox. It started 2 days ago for me. I can no longer access the in-game mod menu at all, and get that same message. I have tried all the so-called 'fixes' I found online with no success, aside from deleting all my mods again, which people are saying doesn't work anyway. Bugthesda f***** up another game with their attempts to re-package and re-sell it, just like Skyrim AE, only worse this time.