I'm playing GRIS on a Mac using an 8BitDo controller. Button mapping has been fine so far. A to jump, X to heavy block. However, I am now at the underground tree level. When the "Hold A" circle pops up I hold A, and all that happens is that I jump. Is this all that is supposed to happen? Or am I missing something?

There is no option to remap controls in Settings -> Controller.

On my PC splaying with keyboard O also get hold A instead of hold spacebar.
Seems like a bugged console port to me.

However I needed to press spacebar and release and press spacebar again and hold it.
So I gues you'll have to do the same with the A button.