I updated my iPad Pro

Assuming your device can access the Internet (using other apps, i.e. Safari / YouTube etc.), please check:

Settings>ScreenTime>Content&Privacy Restrictions>Itunes&AppStore Purchases... are the first 3 options set to "Allow"?

Could you please check also Apple System Status in your country using this link:--> Apple - Support - System Status

Regards

Giulio

Try a forced restart of your iPad:

• iPad models with Face ID: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Power button until the device restarts.
• iPad models with Home button, iPhone 6s or earlier, and iPod touch (6th generation) or earlier: Press and hold both the Home and the Top (or Side) buttons until you see the Apple logo.

Regards

Giulio