Double-check that there are no trailing spaces at the end of the key when you paste it. If the issue persists, ensure you are using the correct version of the extension (FireShot vs. FireShot Pro). Why Upgrade to FireShot Pro?
Here’s everything you need to know about getting your license key and putting it to work. Why Upgrade to FireShot Pro? fireshot license key
Take Webpage Screenshots Entirely - FireShot - Chrome Web Store Double-check that there are no trailing spaces at