The mouse cursor will no longer be visible.
(I also noticed that GIFs were not output properly.)

This phenomenon has been observed in previous versions.
Restarting with the reboot command does not fix the problem, so you need to exit the application once.

The situation when I was checking

• Multiple pico8s were running (other mice were normal)
• The editor was running for a long time
• I was using stat() to get the mouse.
• Sprite sheet was copied from another cart by reload

I've had this happen to me, on the education edition too. As far as I can tell, the mouse disappears when you've had Pico-8 open for a really long time. I've seen it happen without using stat() to get the mouse, copying the spritesheet, or running multiple instances of Pico-8.