Your device isn't compatible with this version?

Tablet is an RCA Pro 10.
Google Play doesn’t offer NF as a selection for this tablet. Finding NF manually, this message appears:
“Your device isn’t compatible with this version.” According to RCA’s website, the tablet is “Google Certified.”
How can I side-load NF until you get the problem fixed?
Tablet info:
Model number RCT6203W46
Android version 4.4.2
Kernel version 3.4.67
Tue Dec 2 093421 CST 2014
Build number RCT6203W46-ANDROID4.4.2-3101-V50-V1.3.51