ssh-agent won't start (even with eval ` `)

I'm pulling my hair out on an ssh-agent issue..

I run a VPS under Ubuntu 16.04 and I setup a private/public key to be able to pull code from my Bitbucket repo. I initialized the repo, it all seemed to work fine, and a couple of days later, when I try to pull again, it tells me that the key is not valid.

ssh-add -l says "Could not open a connection to your authentication agent." - so I figure I just have to restart the ssh-agent.. but I always end up getting the same "Could not open a connection to your authentication agent." message.

me@ip:~/.ssh$ eval `ssh-agent -s`Agent pid 3820me@ip:~/.ssh$ ssh-add -lCould not open a connection to your authentication agent.

I've tried rebooting the machine and attempting again but that's no good.. I've run out of ideas from all the posts I've read so.. any suggestions?