For some reason I can no longer switch between position, sport, & tripod mode during my flights. A message pops up in th Go App but I don't know why I'm unable when I've been able to in the past.

Hello there Silvi-Pi. I am sorry for the trouble this has caused and thank you for reaching out. May we know what is the model of the mobile device you are using please and can you please try to uninstall and re install the DJI Go 4 application for us to be able to isolate the said issue? Thank you.

https://www.dji.com/downloads/djiapp/dji-go-4

Try to update the firmware (again) using the DJI assistent 2 programme.
It might be a bad update from the firmware. It happens sometimes.