Sorry to hear about the issue you are facing with Acrobat. Can you please share the version and platform details where you are facing this blank dialog? You can find version number from Help->About.
Also, please try terminating any running AcroCEF/RdrCEF processes from task manager, if they are present when Acrobat is closed. Then try relaunching Acrobat and check if problem is fixed.
Hope you are doing well and sorry for the trouble.
This issue has been fixed with the new version 21.11.20039 now available. Please update the application from the help menu > check for updates and reboot the computer once and check.