You have probably long since solved this problem. The TX on this breakout board connects to TX and the RX connects to RX!!! The designer probably wanted to make it simple for people like me.
I got your problem on an RPi Zero 2 WH but the reason for that was that I had installed the Enviro+ board and its software on this Pi. When I performed the Pimoroni instructions on another Pi that didn’t have the Enviroplus software on it, it worked fine.