MDE app won't work w my phone?

[FelisLachesis]

The Core Prime should be upgradable to Lollipop 5.0.2 or 5.1.1, which is the bare minimum needed to run the MDE app. If the Over The Air update isn't working, then take it to a store that your carrier runs (i.e. a Verizon store, or TMobile store, etc), and see if they can update it there, for you. The cell phone stores generally have methods that don't require an Over The Air update. Best Buy might be able to do it, as well. I wouldn't count on Walmart or Target to, but Staples might.