SENT Message WAS blocked

This is not an issue of GSM. It’s more a problem with your emails or your address quality. Google see in your emails a spam or fraud problem.
What Google says (
Technical details and how to solve  (more or less usefull)

I want to send more emails / day

Your daily limit depends on your Google account type. GSM has no daily limitation, you send as much as your Google account allows  That means up to 1500/ day.

GSM asks for authoriZation

If you were asked for authorization (additional rights), its is normally needed after an GSM update and you should confirm the request. But in some cases you will be asked multiple times (every time when you open GSM) in such a case it´s better to uninstall and reinstall GSM. Store

I registered my license, how to activate it?

Click in GSM the menu item “License / Register”. This will update your license state and display your license information.

I registered my license, and the daily limit is unchanged?

Registration has no impact on your daily limit (that depends on your Google account type). A GSM registration removes only the advertising line in the bottom and makes your emails a bit more professional.