I had the same issue.
It was working with a newer Android 7.0 Version and stopped
a few days ago.
But it was still working with an older android version and smartphone.
I had the same gueswork like you.
I tried a few setup changes an couldn’t solve the problem first.
Now I decided to try a few hardware changes.
I didn’t have a SD card in the slot yet. So I put a 16 GB SDHC card in the slot, made a reset, connected again and now it is working.
Hope it’ll also help you