Installing Exchange 2019 CU11 downloaded from the Action Pack; product key is no good

A few days later and the silence is deafening.

But in case any search engines pick this up, here was the solution. The EAC continued to return errors. And then I read a little farther into the documentation - there's a Powershell way to enter the product key. Quoting the documentation:

To enter the product key in the Exchange Management Shell, use this syntax:

Set-ExchangeServer <ServerName> -ProductKey <ProductKey>

Note that this command works to license an unlicensed server or to upgrade a licensed server from a Standard Edition license to an Enterprise Edition license.

This example licenses the Exchange server named Mailbox01.

Set-ExchangeServer Mailbox01 -ProductKey 12345-12345-12345-12345-12345  

With nothing to lose, I tried my activation from Powershell and it worked.  The EAC said the key was invalid, but Powershell liked it. Go figure. I restarted the Information Store service and now the EAC says I have a fully licensed Exchange 2019 server.