Windows 8.1 RT wont update

Hello I have a Nokia Lumia 2520 running windows RT8.1 and use the team viewer app, it works great for connecting to  team viewer 11 computers, but when I run the app search to update my tablet, it doesn't come up in the window app store unless I send the link I created a few months ago, via email but the app will not update,  it say its already installed on this computer [Nokia] and when I try to connect to a computer running 12  I get the message the computer I trying to connect to is running a newer version of Team viewer..do I want to update this team view ,  so I say [ok]  but it wont show the app or it say teamvieawer is already installed on this computer, I'm afraid to remove the app completely from my tablet because I might get it back, [I mean at least I can use 11, but I want 12.what can I do , can you offer any help