I have a problem with updating an Android app. My requirements to the application are:

* It must work constantly (24/7);
* Updating should also be automatic, with no user input.

I uploaded the application to the developer console to conduct beta-testing. Then, I installed it on the tablet (I used URL).
Then, I uploaded the update, but the application does not start the updating process automatically. 
There are no added additional permissions. The "automatic updates" are turned on in Play Market settings.
4 days have passed. If I go to the app's page in the market, I see that an update is available, but it does not start the download process.

The question is: what may be the problem? Why does the app not update? 

Is it possible that the app gets reinstalled instead of an update (thus requiring some user input to proceed)?

Thank you in advance!