PS:
Something worked and stopped working for no obviously reason.
We are clueless.
We aren't aware of any rational cause.
If so, trial and error troubleshooting should beginn with anything
half-way reasonable we are able to imagine, even troubleshooting much
unlikely causes.
Actually I experienced both in once for an class compliant audio device
used with iOS. There indeed was an USB power issue, but after solving
this by an active USB hub, it still was impossible to record, just
playback worked. To funny, the same device worked without issues with
my Linux machine. The USB audio device of another vendor works without
issues on my Linux machine as well as on my iOS devices. It wasn't just
an user error, it was the device and/or the class compliant driver that
failed. In my case Linux didn't fail, it was iOS that failed.