I've only recently (around a month ago) switched to GrapheneOS on my Pixel 9 Pro XL phone. While I was still using it as stock android, my sim card / carrier supported 5G on Android.
Switching to GrapheneOS, 5G worked for a little while (1-2 weeks), but then stopped working. I can only access LTE / 4G and slower tech now. I switched the SIM card into another phone (an iPhone), and the sim card there worked fine with 5G. I have also contacted my carrier to discuss if any restrictions have been imposed on custom / niche operating systems, to which they disagreed with.
I have tried using carrier settings overrides, have tried re-inserting the sim card, and approximately everything else besides a factory reset or re-flashing. I want to hold off on resetting my phone unless its the last possible option.
Can someone provide guidance or suggestions? Thanks in advance, and sorry for my bad English as I am not a native speaker.