Opensearch is giving 502 Bad Gateway and Not accessible from anywhere

Opensearch is showing the cluster health in Red Zone and is not responding from the endpoint url and giving the 502 bad gateway.

I tried to upgrade the cluster configuration, still it is showing in progress since last day. It is stuck at 14%. Not sure what is the issue because upgradation is also not happening.

There were 2 nodes in this cluster, but now I am not able to see a single one in the instance health. It was showing free disk space upto 74 GB. And it has very less data. Near about 1 million only.

This is the managed service. Version - OpenSearch 1.2

Opensearch is not working since 2 days, so kindly please help me to make it run again. Because I can not afford to delete this cluster and create new one.