Firmware upgrade for NOUS A8T fails

[wjohn007]

I tried to update my NOUS A8T Smart Plug.
Here's what happened:

The original firmware was Tasmota 14.3.

14.6 OK http://ota.tasmota.com/tasmota32/release-14.6.0/tasmota32.bin

15.0.1 OK http://ota.tasmota.com/tasmota32/release-15.0.1/tasmota32.bin

15.1 Error http://ota.tasmota.com/tasmota32/release-15.1.0/tasmota32.bin, remains in safe mode.

15.2 Error http://ota.tasmota.com/tasmota32/release-15.2.0/tasmota32.bin, remains in safe mode.

How can I fix this?