How to get past the Embarcadero Product Registration Dialog when installing Delphi 10.4 CE

I'm attempting to install Delphi 10.4 Community Edition on a Windows 10 machine which previously had the full version installed (that license is now expired). The previous licence was an Academic licence and these have to be renewed annually. I've followed the instructions from activation.embarcadero.com:

1. First place the file into any folder on your hard drive, My Documents for example.
2. Then launch the product. If your copy has not been activated before, the Embarcadero Product Registration Dialog will come up.
3. Click the Advanced button in the registration dialog. Click on Import. Navigate to and import the license.

However, after I do that, the Registration Wizard closes and I get this pop-up:

No valid licence information found for Embarcadero (r) Delphi 10.4. You must provide a valid serial number to use Embarcadero (r) Delphi 10.4. Do you want to run the registration wizard again?

Registration code 12963955

You are not licensed to use Embarcadero (r) Delphi 10.4.

In case the problem is being caused by a remnant of the previous, Academic version, I've deleted

• the whole of Program Files(x86)\Embarcadero and below
• all the registry keys and values containing 'Embarcadero'
• the Embarcadero folder below AppData\Roaming
• all references in the system path to the Embarcadero and below folders

and I still get the problem.

So I'm stuck. How to get it to accept the registration file and get the installation to proceed?