Hi Lem2kee,
It sounds like your keyboard isn't working on your iPad sometimes. We're glad you've joined us in Apple Support Communities. Let's see if this helps.
First, when this happens, could you accidentally be hiding the keyboard? Check out the section, "Enter text using the onscreen keyboard" and the last bullet that outlines "Hide the onscreen keyboard" in Type with the onscreen keyboard on iPad. This will show you what gesture could be causing your keyboard to hide.
If you review the above information and the issue remains, have you had a chance to restart and check your iPad for updates? Both restarts and updates resolve issues both big and small.
You'll also want to make sure that GoodNotes is up-to-date with the advice in How to manually update apps on your Apple device. Oftentimes, when the iOS version gets updates, so do apps.
If you have a third-party keyboard installed, let's see if that might be the source of the issue. Check out the steps in "Add or delete a third-party keyboard app" in Add or change keyboards on iPad.
If the issue remains after following those steps, let us know which steps from above you had a chance to try.
We hope that helps with your question and take care!