When a single-user license disappears from a computer, the next time you run Surfer, Grapher, or Strater, the program will check for a trial license. If you have not yet run the 14-day trial, it will be activated to use. If you have already used the trial, you will see a message indicating the trial has expired.
The most common cause of an activated Surfer, Grapher, or Strater license disappearing from the computer is a change in the locking code for the computer. Our licenses are locked to the MAC Address, UUID, and CPU Info String. If any of these criteria change then the locking code for the computer will change, and previous activation will no longer be recognized as valid.
The licenses can be restored by deactivating the previous activation through our My Account portal and then activating the license again by entering your product key into the program.
If the computer change that caused the change in locking codes will occur routinely (for example, if you have a laptop that frequently docks and undocks from a docking station), please contact our support team to let us know what locking criteria will be changing. We can then create a custom license that will better accommodate your computer setup.
If your licenses are no longer on your computer, but you do not believe the locking code is the cause, please click the Create support file link in the lower right corner of the licensing dialog and send in the file for further investigation.
Updated November 14, 2019
See here for information about a concurrent-use license disappearing from the license server: Concurrent-use license disappeared from license server.