If this isn't a bug I don't understand it. I can't play what seems to be a valid card, a bludgeon or a walk card for instance. mousing over the walk card shows movement squares, but clicking on the card doesn't use it. no explanation.
Does your character have any traits attached to them preventing the use of certain cards when this occurs?
I have thought of this, but I can't see what it is that's causing some or indeed all cards to be playable. Are there modifiers that forbid movement, but allow the movement arrows on the board to show up? When i'm caught in a net, there's a nice explanation that pops up. I've also seen red boxes with notices about not having a valid target. But It happens at least once every other campaign that i can't move and there's no clear reason why and certainly no pop up notice... what information would you need to call this a bug?
A battle log or screenshot would help: https://forums.cardhunter.com/threads/please-read-how-to-report-bugs.331/