My iPhone 11 Pro running iOS 18.7.1 shows spinning wheel on Screen Mirroring

Have you tried resetting your network settings?

Reset your network settings

If you're using iOS or iPadOS 15 or later, tap Settings > General > Transfer or Reset [Device] > Reset > Reset Network Settings.

If you're using iOS or iPadOS 14 or earlier, tap Settings > General > Reset > Reset Network Settings.

This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before.

John B13 wrote: "Yes it does still have its original battery

Maximum capacity is now degraded to 73%

Next time I am near an Apple Store I plan to replace the battery"

Ok, good. Once replaced, your devices will likely show up instead of that spinner. Meanwhile, don't apply iOS updates — because if the degraded battery completely fails during one, your iPhone may be 'bricked'.

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John ~ As your iPhone 11 Pro could be 6 years old, it's worth checking for a weak, aging battery (which can cause connectivity issues.) So...

Does your iPhone 11 Pro still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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What device are you trying to connect to? Are you sure it’s on the same network?