Sadly Roku support never once suggested this or I would have resolved this long ago.
After a factory reset, which I did to try and fix the PRIME issue of playing the vid in a small postage stamp size in the upper left corner (not sure if completely resolved yet or not), but after I did the factory reset P+ no longer would show the 4k HDR badges or play content in that format on either of my Roku's.
Finally by contacting P+ on Instagram I was advised to CLEAR THE CACHE which is done as follows:
1. make sure HOME is selected on menu
2.using the remote do the following consecutively: Hit HOME button five times (upper right button) then hit the UP button (above the OK button) once and then hit rewind twice then FF twice.
3. And then do NOTHING even though it seems to not be doing anything, it is. Takes about 20 seconds.
This resolved my issue on both of my Roku's, and as far as I can tell Roku support never once suggested this to me. Anyway, it is said that a restart of the device also clears the cache, but I had restarted mine many times and it did not, so this is the only sure way.
You're welcome.