“Account locked temporarily
We have detected unusual activity on your account and have locked it temporarily. Please contact customer service for further assistance.”

Solution Pages:
How-To: Amazon Account Locked? 4 Fixes
https://www.groovypost.com/howto/amazon-account-locked-4-fixes/

Account locked temporarily
https://www.reddit.com/r/amazonprime/comments/18vy1g5/account_locked_temporarily/