Fix: "Product Key Invalid" Error When Installing Exchange Server 2019
If the issue persists after trying the above, open a support case with Microsoft Volume Licensing Support. exchange 2019 product key invalid
If using Exchange 2019 RTM or CU1–CU11, download the latest Cumulative Update 14 (CU14) or newer from the Microsoft Download Center. Newer CUs have better key handling. Fix: "Product Key Invalid" Error When Installing Exchange
Run the following command in as Administrator: exchange 2019 product key invalid
Set-ExchangeServer -Identity "SERVERNAME" -ProductKey "XXXXX-XXXXX-XXXXX-XXXXX-XXXXX" Then restart the Exchange services or reboot.