An update:
We found our old Asus RT-AC3200 router and tried it. The Roku Channel works just fine with that. Confirmation that there's something wrong with the Netgear RAX70.
Thanks for all the help troubleshooting the issue!
We upgraded to the Asus GT-AX11000 and we're back to Roku Channel working on TCL Roku TVs and Windows laptops. Netgear eventually tried helping with the RAX70 but it can't be fixed.
Thanks again for all the assistance!
Good to hear. Since you now have a brand new setup that is working, it is a good time and opportunity to go through your current setup and settings and make a note of the different settings and firmware versions. (known working condition). This way can help isolate if future issues arise. (firmware updates, devices removed or added to network, settings appear changed, altered, no longer available, etc.)
Some router firmware allow you to save settings to a viewable file (that can also be used to restore to previous condition if an issue arises.) Short of that, just screenshots or using a phone camera will at least give you a physical reference for later.
Glad you are back up and running. 👍
Thanks! Asus has an option to save settings, which we've done. We made note of the current firmware version in the filename too. Hopefully we won't run into any more issues like this again.