I'm new to animating in krita and I have this issue where the whole canvas would turn black when I click the play button. When I stop the animation, the canvas is still black and I couldn't draw anything on it. Any ideas why this is happening? Thank you.

Can you check if you have graphics acceleration on in settings->configure Krita->display? (It needs to be on for good animation playback)

And if so, can you tell us a bit more about your canvas? The pixel size? The Color bitdepth? The amount of frames? (Just make a screenshot, everything should be in the status bar)

Yes, Graphics acceleration is on. RGB/Alpha (8-bit integer/channel) sRGB-elle-V2-srgbtrc.icc , 3508x2480 (97.4 MiB).
It's only a 4 frame animation of a squiggly line on a 300ppi(a4) canvas...

Which OS and which version of krita are you using?

Can you post a link to a file download service for the .kra file that is giving you this problem?