iPhone and iPad not showing up for Wifi sync

Hi,

I had to reinstall my MacBook Pro running Bug Sur 11.4.

Since then I'm not able to get my iPhone or iPad to work with Wifi sync anymore. I can successfully sync both devices using a USB cable. I have enabled the option "Show this <device> when on Wifi" option turned on, of course. But still as soon as I disconnect the USB cable the device disappears from Finder's sidebar and does not re-appear even days after.

What I tried so far:

• disable and re-enable the option "Show ... when on Wifi"
• Restart all devices
• Reset the Privacy and Location data on the iOS devices
• Reset Network Settings on iOS devices

Although I had to re-authorize the trust for my computer on the iOS devices again. But nothing got the Wifi sync back.

It seems that the option "Show ... when on Wifi" disables itself after some time. Especially when either the computer or the iOS device is restarted. But not always.

Any suggestions to get this fixed? I want to avoid having to restore the full devices.

Thanks!