I had this problem on my iPhone 16 Pro Max after updating to iOS 27.
When I opened Control Center > Screen Mirroring, it would either keep loading without finding my TV, or eventually show a receiver but selecting it would not actually mirror anything.
My iPhone 13 Pro Max and an Android phone could still mirror to the same TV normally, so I knew the TV and home network were working.
What fixed it for me was very simple:
Step 1: Install FastCast from the app store/app library available on your TV, if your TV offers it.
FastCast did not come pre-installed on my TV. I installed it myself from the apps available to download. FastCast has been completely free for me, and I have never paid anything to use it.
Step 2: Open FastCast on the TV.
Step 3: On the iPhone, open Control Center > Screen Mirroring.
Step 4: Select the FastCast receiver. In my case it appears as “FastCast 82”.
Screen Mirroring then worked immediately and normally. Once connected, I could exit the FastCast app on the TV and mirroring continued to work normally.
I did not need to reset network settings, restart my router, change Wi-Fi settings, factory-reset anything, or change TV settings.
I can’t guarantee it will work with every TV, but if iOS 27 suddenly stopped finding your TV or appears to connect without actually mirroring, it may be worth trying FastCast before resetting everything.
Just to avoid confusion: FastCast is the name of the TV app. “FastCast 82” is simply the name my FastCast receiver shows in the iPhone’s Screen Mirroring list.
Hope this helps someone!