MongoDB no rachable servers (Mongoeye)

Question

I'm trying to use the tool below:

https://github.com/mongoeye/mongoeye

To scan MongoDB collections in order to retrieve unique field names in order to generate proper schema for my databases.

First of all, I'm able to successfully connect to Mongo from the Ubuntu terminal with no problems or errors (I use both a Linux subsystem for Windows and clean Ubuntu 20.04 on a separate device). However, when connecting through the tool above, I get the following error:

I'm using the latest 0.5 release and I don't know what's causing the issue. Here's the connection string:

./mongoeye --host "mongo-etl-proxy.staging.NAME:27017" -u user-etl -p "PASSWORD" --auth-db admin --db sales --col sales

Maybe it's because the connection goes through ETL-proxy? I've seen some suggestions to use mongoimport but I'm not familiar with it.

There are also restrictions regarding access for security purposes but my network/IP has been added to connect freely. I would appreciate any help on the matter.