FYI: I contacted Adobe support directly for a fix, and they don't have a clue. They told me to go to the forum for an answer, as they don't support their android apps. That's pretty sad.
I tried to reproduce the same at my end and seems to be working well.
Request you to confirm the workflow and let me know how do you create the form.
Also if you would like please share the sample form and check the private message i am sending you for the information.
OMG Me too
Sorry for the delay in response.
As you get "Read Only" message when you try to fill the PDF on Android, please make sure that you made the form Reader Extended.
It may be the reason that you are not able to fill the form in Adobe Acrobat Reader mobile application.
Also, check if there are any restrictions added to the file.
Hope that answers your query.
Let us know if you have a different issue.