Onn devices will not recognize USB stick

I set up one of the new Onn Pro devices, I plugged my USB stick in which had 90% of the apps I wanted to put on it, and I installed all of them using X-Plore. I put the stick back in my SK1, and a few days later I needed another app, now the Onn will not recognize it, in fact I tried 3 different Onn boxes, an old Pro and a Plus, Put the stick in my SK1, SK2 or X88 and there it is I can do what I want with it.

I tried USB debugging in and off, turned developer options off, I even copied the files from it and formatted it again to exfat, how it was, and then loaded the files back on to it and it still can not be seen. Odd it was usable for a few days and now it is not,but only in the Onn devices.

Any help is appreciated.

Update, I took a new USB Stick and formatted to Fat32 as that is what everything I read when I searched, it needed to be for the Onn. Still does not recognize it.

Guess I need to see if I can remember how to send apps using xplore over wifi.