Gandy-d Said:
"macbook pro not connecting with bluetooth to iPad or iPhone"
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Troubleshooting Mac Bluetooth:
"Reset the Bluetooth Module":
See my User Tip: Use "Reset the Bluetooth module" to Fix Constant Bluetooth Disconnections - User Tip, Looking at my first comment on it, recommended to Apple that they bring this option back. They discontinued it on ealier macOS versions.
What else to do:
Try the following, in the order provided...
[Hold Down: shift key, upon boot], In Safe Mode, Login Items do not run at login, certain preferences are set aside, and damaged system files are then reset. So, once booted in to Safe Mode, wait for 30 seconds, and then boot up normally, attempting another sync.
What happens when you create a new administrator user, and log int it? Do you still get this error? If not, then it is likely an error with the current user. If so, then it is likely an error with your macOS.
as a last resort...
Go Here: How to Reinstall macOS from macOS Recovery - Apple Support
Important: First, Back Up your Mac:
Create a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with the reinstall. Take this as a learning experience, knowing to always create a backup of your Mac, prior to making any major changes to it (i.e. update installation)