Migration Assistant “This Mac is attempting to reconnect to your Source” when restoring from a USB Time Machine backup

CousinDirk wrote:

I have a new MacBook Pro and I am trying to set it up by migrating from the Time Machine backup of my dead iMac, which is on an external USB hard drive.

On my first attempt I left it running for many hours and came back to a pop up saying “This Mac is attempting to reconnect to your Source,” suggesting perhaps that the hard drive may have unmounted or be having problems. After leaving it for a couple of hours more I unplugged the drive and let it rest for half and hour before plugging it in and trying again, but nothing happened.

I plugged the drive into my work MacBook Air and it mounted without any problems. As a precaution I ran First Aid using Disk Utility, which took a few hours but seemed happy with its work when it was done.

Nothing happened when I plugged the drive back into the new MacBook Pro so I cancelled the transfer, went through the setup of the laptop, then ram Migration Assistant again. It seemed to run quicker this time but it still ultimately kicked up the ‘attempting to reconnect’ dialogue. This time I left it in this state for a good 8 hours to see if it would recover itself but to no avail. I disconnected and reconnected the drive and left it again but nothing has changed.

I have a few questions.

First, is there anything else I can try to get this to work, short of just trying again and seeing if there’s a different result?

Is it worth just trying again and seeing what happens?

And finally, if this doesn’t work, what will I lose by just setting up the machine as new and manually copying over all of my files and reinstalling software?

The most trouble free way to move to a new machine, is using the Setup Assistant on the initial boot of a brand new machine— you have one shot here. Set up your MacBook Pro - Apple Support

The second best way is use the Migration Assistant.

How to move your content to a new Mac Move content to a new Mac - Apple Support

If the backup is failing you try another backup soutce and compare your results...

If you value your user data

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

More than one device, more than one backup methodology.