Comment by mike_d

You can contact support by signing in as the domain admin to admin.google.com and clicking on the question mark in the upper right.

Do you have sales people? Enable any "mail merge" or "customer contact" apps lately?

Google rarely shuts down Gsuite domains without a good reason. If they really aren't telling you the reason - it is abuse related.

(Former Googler, opinions are my own, etc etc)