So originally I had paid version 3.4 installed on this tablet. I removed that and then installed the free version. I then uninstalled the free version and the tablet is now clean. Attached are some pictures of the situation. I don't think this is device specific as the web browser on my PC also thinks all of my Sero 8's are incompatible with this version. Do you have some region restrictions on this app? Are you sure you have the Android version set properly on the store for the paid version? On these tablets it only lists the free version as available, the screenshot on the tablet is from the 'my apps' section as I had bought the paid version on that account.
FYI, it appears that your free version is stuck at version 3.3 and was updated last early 2015. I am sure you know this, tho.