iMac does not recognize iOS devices ("AppleUSBHostPort::disconnect: persistent enumeration failures")
An old (mid-2010) iMac 27" with MacOS 10.11.6 behaves quite normally otherwise, but ignores iOS devices (tried with iPhone 12, iPhone SE1 and iPad mini 2):
- They do not show up in the system profiler as USB devices
- The devices do not even recognize the iMac as charger
- A single time I got the message to unlock the phone to connect to the device, but I could not reproduce this
Basically it's like there is no connection at all, but
- All devices behave normally on a MacBook Pro 2012
- I tried with two different cables (both work on the MacBook)
- Other USB devices behave normally on the iMac, including an external hard disk drive, so it's not a question of VBUS power supply either
iMac works, USB works, VBUS supply works, cable works, devices work. What other cause is left?
I only need a one-time-connection to pair the devices to get them to sync via WiFi.
Please, before marking this as duplicate, check the sypmtoms are really the same. I did not find an answer among similar questions.
Update: In the konsole, when plugging in one of the devices, I get
11.10.21 16:43:37,000 kernel[0]: 049596.304561 AppleUSB20HubPort@fd130000: AppleUSBHostPort::disconnect: persistent enumeration failures
El Capitan is pretty old you might need to update the machine High Sierra which is the latest Apple certified version to work with a mid-2010 iMac.
Otherwise here are some steps you might want to try:
Rebooting the iMac
Ensuring the devices are unlocked when plugged in.
Do you have iTunes on that iMac? The software might be old enough that it's required to sync the devices.