This is the second time my (2015) Macbook has failed to recognise devices attached to an Apple USB/HDMI adapter. The fix is an SMC reset ( https://support.apple.com/en-au/HT201295 ) but I hope it does not indicate a failing motherboard or similar!
Symptoms are failure to mount an external hard disk and failure to connect to an external display via HDMI. It may be worth connecting them from time to time to check the Macbook.
I have tried other adapters and they also don’t work until the SMC reset.
I will try to keep my backup SSD disk up-to-date while travelling - just in case!