Why is my iPad not accepting my passcode?

Possibilities: your recollection of the passcode is incorrect, the passcode was compromised and changed by somebody else with device access, or the display or digitizer hardware is failing. Maybe a problem with protective film or the case, if either or both are in use here.

How to reset with a computer:

• If you forgot your iPad passcode, use your Mac or PC to reset it - Apple Support

Without:

• If you see a iPhone, iPad, or Apple Vision Pro unavailable message or Security Lockout screen - Apple Support

The reset will erase the current contents.

Having cleaned up the debris after folks having loaned their devices to their younger relatives, I’ve seen precious photos permanently deleted, obscure settings corrupted, subscriptions cancelled, passwords copied or clobbered, and assorted other data mayhem. More than a few of the wee bairns are quite experienced and savvy about exfiltrating passwords and causing selective destruction, too.