I am unable to connect to my Apollo (graphql) server through Apollo Studio (https://studio.apollographql.com/sandbox/explorer) OR Apollo Client library on frontend. But the server is working fine when a request is sent through Postman, graphql-request library OR a CURL request.
Details of Deployment:
The server is deployed on GCP instance groups which include 4 instances in two different regions. I have used Nginx as reverse proxy to redirect traffic to localhost:4000 of each instance (the app is running on port 4000 of each machine). The instance groups are attached to the GCP HTTPS load balancer. The backends are in the healthy state in the load balancer.