Problem:

SFTP is asking for a passphrase when attempting to make an SFTP connection in Everbridge Suite.

Root Cause:

This is most likely due to the format of the key not being accepted by your SFTP application, specifically an application executed from the Linux or Unix command line. The link below explains the behavior:

https://serverfault.com/questions/969194/sftp-asks-for-passphrase-for-unencrypted-private-key-but-winscp-works-fine

Solution:

Convert the key to RSA format. The link below (also referenced in the above document) explains how to convert the key to RSA format:

https://www.tbs-certificates.co.uk/FAQ/en/putty-ppk-vers-openssl-openssh.html