Surf-On-The-Go Problems With 5GHz Connection

Hi - I’m attempting to connect An Amazon Fire Stick to a PepWave Surf-On-the-Go router that is set up for 5GHz, but the Fire Stick does not see the access point. It will connect if I re-configure to 2.4GHz but the connection is too slow and inconsistent to be useable. All my other devices (iphones, PCs) see and connect to the 5GHz wifi without issue.

I have read several posts about setting the 5GHz channel to 36+ to get the Fire Stick to work at 5GHz, but
I have not been able to figure out how to set the router to a specific channel. The manual shows an “AP Channel” setting, but I do not see that in the AP settings on my router. What I do see is a Selective channel scan setting that allows you to limit the 5GHz frequencies that are scanned . I did get the Fire Stick to connect once when I limited the channel scan to one of the lower frequencies, but it then would not connect to the Marina wifi that it is acting as a repeater for.

Any advice or ideas?

…phil