If your seeing the following screen "App is blocked" when logging into Google there is an easy fix for you.
First go into your Google account and click on "Data & Privacy" in the left hand column:
https://myaccount.google.com/data-and-privacy?authuser=0
Scroll down to "Apps and services" and click "Third-party apps & services"
Scroll to "Get It Done Tasks" and click on that item.
Next click "See details" under "Get It Done Tasks has some access to your Google Account"
Next click "Remove all access"
After doing this, you should be able to log into Get It Done again.
If you are still having problems logging in please open a support ticket, thanks!