Android paid Prime app refuses to install

[DA74254]

Hello,
I've searched the forum, but came up blank..

I have a Cat s60 with Android 6 installed.

I have the Prime free app installed and it functions as expected.
However, I purchased the Pro version and it downloaded as expected but came up with "installation failed" - Twice. I then asked for refund within the 15-min rule and received that, so no money lost :-)

Anyway; anyone else having trouble installing the Pro version?
My phone seems not to like the Pro, though it happily runs the free version.