The extension license should automatically change to the Full license after you purchase the extension. If it did not change the license automatically after you purchased it then please try these steps in a row:
Click on the extension icon. Scroll down to "License Key" or "Order ID". You may need to enter your order number or license key that was emailed to you in the "Order ID" field.
Click on "Check". If the "Sign in with Google" screen appears then you must click on "Allow".
When Chrome has reset then make sure that you first sign into Chrome with your Google account. Make sure sync is on. Then reinstall the extension from the Chrome Web Store and follow step 2 again.