Thank you for posting your query here. Please help me with few details to understand your issue better.
Make and model of your device?
Application version?
Are you having issues with the same pdf or all the pdfs?
We did try to replicate the behavior on our end, however, it is working fine. Make sure your application is updated. Do save your work then try to sign out and sign in back. Reboot your device.
For iOS Adobe Reader Mobile verion: 21.03.00
For Android Adobe Reader Mobile verion: 21.3.0.17414
It's not clear what your issue is. Have you been trying to open the same PDF in the Acrobat Reader for Mobile for two weeks and it won't open? Can you open other PDFs? Can you open that PDF on another device?