If you have a subscription VUL license then backups stop working, restores will always work. If you have a perpetual license, VUL or socket based, you can still backup and restore

You have a grace period. Regardless, restores never stop. Accentuating, backups will. At a minimum, you'd have a 10 VUL license (as is in Community Edition). 

An explanation can be found on this page at the bottom under Grace Period - Updating License - Veeam Backup Enterprise Manager Guide

Grace Period

Veeam Backup Enterprise Manager supports a grace period after the license expiration date. For subscription license, it lasts for 30 days, for rental license — 2 months. During this period the product will be running, but a warning about license expiration (grace period) will appear on the Dashboard tab and in the sessions information.

You must update your license before the end of the grace period.

Messages that can appear in the automatic license update session log are listed in the License Update Session Data section. Similar messages are received as pop-ups after you force the immediate update.

Here's info from the VMware user guide:

https://helpcenter.veeam.com/docs/backup/vsphere/license_grace.html?ver=120

Restoration won’t be stopped, regarding backup, it depends on the license type, subscription will be stopped, perpetual won’t be