Offline deactivation of a online activated product

We have a costumer who seems to have activated a product of us via online activation. Now their server hasn't anymore a internet connection, so they want to switch to an offline activation. But they are unable to deactivate old key.

Error message: "Connection to the server failed."

Is there a way to delete the key from their server even without internet connection?

a. Use the latest version: https://wyday.com/limelm/help/faq/#update-libs

b. All of the functions are listed in the particular integration files for your programming language. For example, in TurboActivate.h search for "Deactivate" and you'll find 2 functions: TA_Deactivate() and TA_DeactivationRequestToFile()