Hello
The biggest problem here is that you unlinked the old device from your MIcrosot account, that means the transfer troubleshooter will not work anymore and only support can help you transfer and link it back.
To get help, open the "Get Help" app on your computer (just search for it in the Start menu). or go to https://support.microsoft.com/contactus, Type "Billing" and press Enter. On the next screen, click "Contact support" at the bottom of the page, then choose "Windows" > "Manage my subscription". You’ll then see the option to chat with a Microsoft support agent who has access to your account to help review the issue.
In the future, you can transfer the license, but when you used the generic key, you need to disconnect internet for it to work, so that Pro is installed onto Home. Then run the troubleshooter.
Also, I don't know if you got the Pro upgrade license or full license. If it is upgrade license, it must be used on an Home edition that's already activated.