If you’re using the Apple Business Manager (ABM), you should have received an email stating that you need to accept the new Terms and Conditions.
It’s important that you do this to be able to continue enroling devices and deploying out applicatons.
Simply log into ABM at https://business.apple.com/ and you’ll be presented with new T&C’s.
You can take a read from within the portal, or download as a PDF to read offline.
When you’re ready to agree tick the agreement box and then the Agree button.
It’s as simple as that.