BPi M2 Zero: voltage on Rx pin?

Just tried to setup UART on my Zero by following instructions from this thread [Banana Pi M2 Zero] How to enable UART? but it didn’t work for me.

Then I decided to try another serial port - the 3 holes to the right from microSD, that is. I checked voltage (with a multimeter) on the Rx one - the port that should be 0V as far as I understand how UART works - and got about 2.9V! Tx gives 3.23 btw.

I also did the same thing to pins I was originally trying to connect to (pins 8 and 10 I believe) - same 3.23 for Tx, but Rx is now 0.03.

Are my serial ports broken or something? Help!

Still hoping to get some help here