Error Message when you are trying to renew an existing cert or generate a new cert:
The client lacks sufficient authorization :: Error creating new authz :: Validations for new domains are disabled in the V1 API(https://community.letsencrypt.org/t/end-of-life-plan-for-acmev1/88430)
This error is caused by old version of certbot. You can simply upgrade your certbot to resolve this issue.
apt-get install --only-upgrade certbot