First of all, thank you for your reply and for that link. I have tried a few things and it ended up that the issue was my private key. The private key was OPENSSH while the requirement was an RSA key. After converting to RSA, the connection went through fine.

For reference, I used the command 

ssh-keygen -p -P "old passphrase" -N "new passphrase" -m pem -f path/to/key