We have found an issue with this IP block on our end. There is an ACL called by a service policy that currently includes this block of addresses. The automation that updates this ACL will change in 2 weeks to include this block, and it would start working at that time normally.
I would rather not keep you waiting 2 weeks for this to resolve. If you're open to changing this /30 to another block, I can get this working sooner. Please let us know if this is acceptable to you.