I try to upgrade Plesk 7.1.7 to 7.5.4 with Updater, but I get message:

"Plesk is unable to update your product license.

Empty error message from utility.

Continuing with the upgrade without having an appropriate product license will result in the installation of a default license with limited functionality. Administrators are advised to first acquire the appropriate license before continuing with the product upgrade.
Confirm skipping of key update and installation of the default key"

I didn't want to check "Confirm skipping of key update and installation of the default key: because I was afraid that after that PLESK would.t work properly. I need upgrade because my license key expire on November 12, and EV1 doing licence key upgrade only after installing 7.5.4. I don't now what do! Can anybody help me?