Hello. When you reinstall license, it is very preferable to delete CodeLib file(s) located in "Shared" folder, start ZM to let it autoupdate (it will download empty license storage file) and restart, then perform activation of ZModeler with your new license key. It could be preferable to set up online validation, so ZM can download license key and perform validation automatically.
If your copy is unable to reach updates server (updates icon is keep spinning in the bottom of ZModeler window), you can use offline activation method only (copy + shift), and this method will work for the very latest build only: Build 1127 to the moment.
Let me know which of above does not work, I'll try to assist.