GCP pub/sub subscription unable to add push type subscription to trigger cloud build

I am a GCP noob and trying to restore a project on GCP which was marked for deletion.
Everything else was restored successfully (that is what I think, could be wrong) but the pub/sub topic and subscription were missing.
There is a trigger that will initiate a Cloud Build in response to a pub/sub message.
I am trying to create a push type subscription for a topic in lower environment to an endpoint which looks like "rpc://name:CloudBuildPushEndpoint:gslb:google.pubsub.v1.cloudbuildpushendpoint....." in prod (and is working fine in prod).
I have not worked too much with Pub/Sub to be very aware of this configuration but whenever I try to create this subscription, I get an error -

I have spent hours searching for something which even looks remotely related to this so that I can have some idea on what could be wrong or in which direction should I proceed.
Appreciate any help.

P.S. I have owner privilege to this project.

The operation is failing because a push to that type of endpoint can only be created by another Google service. You would have to recreate the trigger in Cloud Build itself rather than trying to recreate the Pub/Sub subscription manually.