Not sure if this is an issue with all the flip cards but would play Concoct, get a copy back as Connive and flip it over to Concoct again, however when the copy cast it would cast as Connive and since there were no valid targets on the board it would drain the mana from the card and stay in my hand without casting.
I did get it to work eventually when it was full mana I would cycle it thru Connive/Concoct and that seems to have resolved it. (This was during the last round of the match so not sure its a work around as I only got to try it 1x).