Sometime when I;m playing gwent the game refuses to accept space as input so I can pass and it forces me to keep playing all my cards until I am out. This has happened several time now and I don't know why. Can someone explain it to me ?

Do not know if you have searched this may or may not help.
https://www.primagames.com/games/witcher-3/tips/how-play-gwent-witcher-3-wild-hunt

That does not discuss what I am describing.

Seems from others it is a known bug. Odd such a simple bug wouldn't have been patched after all this time.

The specific method to reproduce is to play a game to a try. Then hit space to play again. Now when playing you will be forced to play all your cards since neither space nor clicking on the hold option will work. Once you have played all your cards you will auto pass but then the computer can easily win the next two rounds (because you have no cards left) and claim the match.

Very annoying bug.

I had the same problem a couple of times. I click with the mouse on the "Pass" button above the avatar and it let me pass my turn. Hope that helps.

(I know this is an old thread but it's 2020 and this is still tripping people up!)

I read elsewhere that you have to hold down the mouseclick for a few seconds for it to be accepted. I have not tried this so I don't know if that's true or not.

Frustrating when trying to learn the game!

Once I held for a few seconds there was an obvious countdown and then I successfully passed. This must be some form of system to let you change your mind.

There was a bug where holding down the space bar made no difference. I'm not sure if it was fixed, but TanguyLOZ's solution worked if it was bugged.

I haven't used or tried the Space Bar if that is supposed to activate Pass. Click and Hold Mouse works and is used in a couple of different places as far as I can see.