Sounds like you have this setup the same as your other two providers?
I would start by connecting a laptop to the new service and set this up with the static address provided and run a test to verify that the service itself is working. Once this is up we know for sure the issue is configuration.
Next I would try moving the new ISP interface into a separte routing instance with its own default route. then run the ip address ping tests from there to verify access independent of the other ISP on the SRX.
Once this is verify we would move on to integrating the new ISP. For this we need to understand how the routing and either failover or policy based routing is working with the existing ISP.