The new iPadOS introduces some improvements to the Share Sheet and makes it a "Smarter share sheet," which is a quick way of sharing content from one app to another faster. However, there are cases when a destination app won't show up in the Share Sheet because the user hasn't used it yet for the system to learn your usage patterns.
To address this issue when you're importing supported files (PDF/PowerPoint/Word) from another app, scroll the top row of apps all the way to the right, tap More (...), tap "Edit" and tap the green plus button next to "Copy to GoodNotes." Tap Done.
Using GoodNotes on a device managed by an organization (University, School, Company)
In some cases, GoodNotes may not appear in the Share Sheet because the organization that manages the device you're using hasn't enabled third-party app access. Please ask your IT department to verify and enable GoodNotes to accept and share documents from/with other apps.