I can't get the new hubitat app to add devices or show unsupported devices correctly for example I have temperature sensors that use custom code to work tuya that show up as unsupported devices but they work in the old app just fine. I can't even get it to add new devices either. Is there any way to fix this
I'm guessing you're seeing this in the Rooms section, if so just go back to your dashboards or the device page itself; chances are they still work just that the Rooms app doesn't know how to work with them yet.
Adding to the above, no version of the Hubitat mobile app has ever allowed you to directly add devices except Z-Wave Smart Start devices (and soon Matter over Wi-Fi devices, or now if you happen to be in the mobile app and hub betas, which you do not appear to be). Any other kind of device administration would just take you to the web UI, which you can use the app to get to but is really just getting in the way; it's normally easier to just visit your hub's IP address in any web browser on any device on your network, or use findmyhub.hubitat.com to search for it if you're not sure.
That said, can you clarify what you mean with it not working for you? Good questions to start with include: how are you trying to add the device, what manufacturer and model of the device is it?