Error : "Could not connect to any servers in your MongoDB Atlas cluster"

Are you using proxy?? please try with different internet connection first.

Try doing this:- MongoDB Atlas -> NetworkAccess -> Edit -> Allow Any

This worked for me!

Follow below steps:
1] Go to https://www.mongodb.com/cloud/atlas
2] login to your mongodb atlas account
3] Click on network access

i] if you have already added ip address, then here you can see ip access list
a] click on delete 

ii] if you have not already added ip address, then just follow below steps:

4] click on add ip address
5] select 'add current ip address' or if you want you can also select 'allow access from anywhere'
6] type in comment if you want
7] click on confirm button
8] this will show pending loader, wait until it shows active status
9] now restart your server on terminal by typing 'npm start'

-- That's it!