This was in single player mode. I played a Sprightly Scarab, and instead of being offered the two usual choices I was shown two card backs, neither of which would let me click. After a few seconds the scarab un-played itself back into my hand. I tried again, and was given two small coin icons to choose from, with similar results. I gave up trying after that and played another card.
I’d played a few (3?) scarabs earlier in the game with no problem. I had several reborn minions, but at least one that was not yet reborn.
I’m not sure what else may be useful. I was playing Beasts. On tier 5 or 6, toward the end of the game. Had a few other cards in my hand including a golden triple parrot. Rivendare on board, the wolf, the bird that gives stats when beasts are damaged, the sea creature that gains health when beasts are damaged, and the taunt minion that does 3 damage to everyone on deathrattle. Oh, and golden reborn mecha-horses with the smaller horse deathrattle, and a golden reborn raptor that summons the 14/14 beast on deathrattle. (Sorry, can’t remember all the names.)