I am having the same issue with my iPhone 14 pro max,post iOS 18.1.1 update,my cellular service is not showing for both physical sim and eSim,tried every options from the forums,swapping airplane mode back and forth,full restore,DFU restore,received a new eSim from the provider,nothing worked.when trying to install the eSim,it gets stuck in the QR Code scan process and I have to forcefully close the window,then it keeps trying in settings under cellular service but I can't switch off.Today I observed a funny thing where some cellular features showed up under my physical sim settings and then disappeared.I am on WiFi now for the last two days without cellular service, the apple support check tool is reporting as a hardware failure,I am frustrated with apple products now,a software update causing a hardware failure,you don't get a rollback option if an update is not working.If anyone find a solution or faced the similar situation,please be kind enough to share here.