connecting 2.4 Nextion to Arduino Pro Micro

I connected a 2.4 Nextion to a Arduino Pro Micro, yellow on TX0 and blue on RX1.

Power and ground are connected separately with a USB connection.

I am trying to upload out of the Nextion Editor (because I can’t find the Nextion Uploader) but keep getting the error: “Connection failed, Forced interrupt”

I am sure I am using the correct COM-port

What am I doing wrong?

p.s. also tried it with a Arduino Nano, same result.