1. Try pasting the key again
This error usually appears because the license key has not been pasted correctly.
Please try and paste the key again, and make sure there are no spaces at the beginning, end, or in the middle of the key.
The key should start with a "2-" or a "3-" so please include the whole key starting from here.
Note: "3-" keys require version 2.18.4 or newer.
2. Try to refresh your browser
This error may also appear when there are caching issues. Please try refreshing your browser or close your browser and try again.