Try this first
Saferow Pro covers all your Macs
On each Mac, open the license email and press Activate Saferow on this Mac, or paste the license in Settings › License. Settings › License › Your Macs lists the Macs on your license; Release one you no longer use and it goes back to Free. If Saferow says the license is on all its Macs, release one there, then press Activate again. Nothing on a released Mac is deleted. A Mac you no longer have can be released on the web, signed in with the email you bought with: Account › Saferow › Your Macs › Release.