The selected source cannot be used for migration error. What do I do?

I assume you are talking about Applications -> Utilities -> Migration Assistant -OR- you are attempting to migrate your content during initial system setup?

How are the 2 systems connected?

• Ethernet direct connect
• Ethernet via the router or an Ethernet switch?
• WiFi
• Other (firewire, Thunderbolt, etc...)

Or are you trying restore from a backup?

Can you give us information on what app is running (as in, is this during initial system setup, or running Migration Assistant, or are you trying drag & drop, restore from Time Machine, restore from another disk, etc....)

This is a horrible bug. Trying to transfer info between two High Sierra Macs. No go.