M5Stack Basic Core stopped working

[j-j]

I've been using the Basic Core for a few months without problems. Today I took off the bottom and reattached it, and suddenly the unit no longer works.

symptom: when bottom is removed and Basic Core is plugged into USB, the 3.3V and 5V signals are very low (less than 1V). The USB device is still visible from my computer, but connection by esptool / M5Burner erase is not successful.

I tried two different USB cables, two different computers.

Please advise.