Hi Renee!
Sorry to hear you've run into this setback!
To clarify, is this the only Rise course experiencing this behavior? Also, do you mind sharing a screen recording of the issue as you are experiencing it on your end?
Testing this in Rise 360 (with Chrome and Edge) I was able to edit all course text without issues. Thank you for sharing the troubleshooting steps you've tried so far. I would like our support engineers to step in and have a closer look, so I've opened a support case on your behalf. You're in great hands troubleshooting with them, and they should be reaching out to you shortly!