iPad won't update pas 10.3.3

Your iPad (most likely an iPad 4th generation) cannot support iOS versions beyond 10.3.3, because of hardware (CPU/RAM) incompatibility, sorry.

Regards

Giulio

If it's running 10.3.3 it's very likely an iPad 4 released in 2012 and incapable of updating beyond that. It's a 10 year old device at this point.

Link-> Identify your iPad model - Apple Support