I have the same issue. So far, I could circumvent it by exporting and importing the deck and the issue was gone. Now I try it with my Standard Merfolk deck but to no avail.

Same here, I have all the cards however no matter what I try, it gives me a warning that I don't have all the cards necessary for this deck. When I hover over the deck it says two rare card but couldn't seem to find what was the problem even after taking out the rares it still gave a warning that I didn't have the cards, and hovering over it said I was missing 2 rare cards. (First 3 images [43-45] for original deck that I couldn't create, next 2 [46-47] are for a deck I made with 0 rares still getting the same bug.)

PC Win10

Deck says invalid when I have all the cards to be able to build the deck. So basically while I was building some decks I found that even though I own the cards it gives me a "Invalid Deck" warning. "Teferi, Time Raveler" seems to be one such card that I cannot put into any deck I build regardless of the number of the card I put in my decks. So far I have seen 3 of these cards in total but I am sure there are more. Also for some reason i cannot add image files (png, jpg...) to this. But I have some screen shots and the deck lists if you want them.

I cannot build any deck at all, I have the cards for the decks, but every time it says "Wildcards needed to complete: x" - but I still have those cards and couldn't craft them with Wildcards if I wanted to, because I still own them.
So what's the point in playing, if you cannot build decks anymore? I don't get it, why I'm not allowed to do this anymore :-(

Same here:

I'm getting the same thing. Here's my log.