How to change baud rate for Telem1?

Did you change baud rate on Qgroundcontrol or mission planner?
Btw you can connect via USB, then open qgroundcontrol, go to mavlink console and send the command “mavlink status” to see if the mavlink istance is correctly starting (baud rate). If that is ok, it is probably an issue with the telem module or wrong baud rate on qgroundcontrol/mission planner.