Why doesn’t my keyboard come up when I’m asked to login or search on some sites? Never had this problem please help.why isn’t my keyboard coming up when I want to write something or when I need auto fill?

Try a "forced" restart of your iPad, using these instructions:

• On an iPad with a Home button: Press and hold the top (power) button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top (power) button. Only when the Apple logo appears (it might take 10-20 seconds), release that button (ignore all other screens that might appear, the one with the "slider" to turn the device off included).

If the issue persists, contact Apple Support, using this link:--> Get Support

Regards

Giulio

P.S. If you haven't already, I would suggest updating your unidentified iPad model to the latest iPadOS version (now 15.4.1).