Copy paste not working

If your iPad is not operating or performing as expected, try a forced restart - as this will often clear an isolated software issue:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)

Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.

If the problem remains unresolved, perhaps you can explain precisely what happens when you try to copy and paste - and include details of the App (or Apps) which which you are having difficulty.

Writing an effective Apple Support Commun… - Apple Community

The more detailed your explanation, the more likely that contributors may be able to offer explicit guidance.