We are sorry, you're having difficulties. Please help me with few details to understand your issue better.
Make and model of your device?
What is file format, name and size?
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 Android Adobe Reader Mobile version: 21.4.0