After you have activated ExtendSim, the Activation Dialog should not appear again spontaneously. When that does happen, the first instance was usually preceded by an error message. If there is only a backup license file (extendsim.lic.bak) in your Documents\ExtendSim folder, try removing the ".bak" and launch ExtendSim again. This will often cause the original error message to appear so you can send us a screenshot.
Below are the most common reasons an Activation Dialog would appear again after ExtendSim has been activated:
Our Support Team can help determine if any of these situations applies to your license.