- The 3.3V control signal from XIAO appears to be amplified by the transistor circuit on the SSR board to drive the SSR. Therefore, it might work even if XIAO’s HIGH is 3.3V. You should be able to check this with the LED on the board—does the LED turn ON/OFF?
- The SSR board seems to require 160mA of current. What is the output current in amperes of the 5V power supply you are using?
Please explain clearly and in detail what you did and what happened. I might be able to think of something.