We are using MongoDB and the connection was working fine with dev and prod DB. suddenly the prod DB lost the connection and showed the below error.
Unable to connect. Error: Could not establish a connection. Try checking your database firewall configuration and whitelisting Retool's IP Address
The IPs are all whitelisted already. The Dev resources are working fine.
Hi @naveenrajv 
How strange! As a quick test, if you create a new resource with the same prod credentials, does it work?
Also, I don’t think these changes are necessary until Nov 12, but have you updated your list of IP’s to whitelist for Retool?
https://updates.retool.com/en/changes-to-retools-ip-addresses-for-cloud-and-on_premise-connections
Still facing the same issue while trying to create new resources with prod credentials.
Got it, thank you for confirming! Do you happen to know what Mongo version you're running?
I am still facing the same issue with my SMTP connection. Please help urgently.
Error message
Unable to connect. Error: Could not establish a connection. Try checking your database firewall configuration and whitelisting Retool's IP Address
Hi @anilr! Definitely happy to help. Is this a new connection or was it working before? Have you whitelisted our new IPs (we changed them around Dec 1, 2022)? https://docs.retool.com/docs/allow-retools-cloud-ip-addresses
Victoria
This connection was working and suddenly stopped working. I tried to allowlist the IP but it didn’t work. BTW this is self-hosted instance as AWS EC2
AR
Ah, got it! In that case, have you whitelisted the new self-hosted IPs? 
https://docs.retool.com/docs/network-storage-requirements
@anilr Also, note the subnet mask!
35.90.103.132/30 means 35.90.103.132 through 35.90.103.134 and 44.208.168.68/30 means 44.208.168.68 through 70. The ones with /32 are single IP addresses.
This bit me yesterday before I figured it out - my IP theory is a bit rusty.
Thanks for your post. For my self-hosted EC2 retool instance I have added the following IP in my VPC inbound rules and the SMTP connection is still not working. Please help.
13.66.251.59/32
13.66.159.82/32
35.92.202.168/29
44.211.178.248/29
Thank you for doing that! I dug a bit more into the SMTP integration and it looks as though SMTP submission needs to be enabled on the Microsoft side - can you check this link and let me know if it's relevant to your setup?
I think i am doing something wrong. I added new ip list. After that I run this API which you can see from screenshot. But API returns 35.90.103.134 not 35.90.103.132 .
Hey @essatav! Hmmm. Is your api working properly otherwise?
facing same issue error mentioned below
Test connection failed (15.509s):Error: Could not establish a connection. Try checking your database firewall configuration and whitelisting Retool's IP Address.
n {statusCode: 422, payload: Object}
statusCode: 422
payload: Object
1. statusCode: 422
2. error: "Unprocessable Entity"
3. message: "Could not establish a connection. Try checking your database firewall configuration and whitelisting Retool's IP Address."
4. data: null
Hey @Abdul_Rafay! Are you seeing this error when you're connecting a new resource? Would you mind sharing a screenshot of the resource setup page?
Test connection failed (16.028s):Error: Could not establish a connection. Try checking your database firewall configuration and whitelisting Retool's IP Address.
n {statusCode: 422, payload: Object}
statusCode: 422
payload: Object
Hi @usman.maqsood! Would you mind sharing a screenshot of your Retool Resource setup page for the SAP Hana DB?
