Is this your first use of Organizer with this scanner or a case where page setup has always worked in the past until now. This Apr/2018 "Importing photos from scanners" guide from Adobe may help sort things out if you're just getting started.
Out of my bailiwick, Oliver. See if resetting preferences in Organizer straightens things out. If I understand, you could scan from within Organizer in times past but it suddenly doesn't work? Go to Edit >> Preferences >> General and click the Restore Default Settings button. Verify your HP scanner is recognized and selected in preferences too.
You may already know that an HP provided plugin is necessary in order for Organizer to control your scans - not to be confused with the stand alone scanning software HP also provided you with. It might be called a TWAIN driver/plugin or have WIA in its name, something of that sort. I always use stand alone software, sorry I can't be more helpful.