Hope you are doing well and sorry for the late reply.
I hope you have solved the issue by now. If you are still experiencing it. Would you mind sharing more details as listed below:
What happens when you try to use the Acrobat Reader mobile app? Do you get any error message? If yes, please share the screenshot of the same for more clarity.
What is the workflow/steps you are doing? A small video recording of the same would be very helpful.
What is the version of the Acrobat Reader mobile app and the OS you are using? Tap on the profile > About Acrobat and try updating it to the latest version available on App/Play Store and reboot the device once and check if that helps.