Validation Failed: 1: this action would add [2] total shards, but this cluster currently has [2000]/[2000] maximum shards open

Elastic Stack Elasticsearch
4

Thanks.
The TLDR is that you probably have too many shards, it looks like your average shard size is only 1.7GB, which is pretty small.

You should look at the _shrink API, and perhaps alter your index sharding strategy.