Hi sherdson1,
Your issue had been posted quite a long time ago. When I ran into the same issue, I thought a reply might still be helpful, iIf not for you, than maybe for others.
I had SnapMirror Progress Monitor v3.0 running flawlessly with five filers for quite some time. Then, out of the blue, it did fail on one of our NetApps, obviously not able to log in, with the result code "null". Strange. I tried a lot of things, nothing really helped, and I admit I still have no real solution. But I might have a workaround: I intentionally provided a wrong passwod, let SnapMirror Progress Monitor retry a connection and let it fail. It came back with a pop-up, asking to provide the password again. Now I provided the correct password, - and o lala -, it worked.
Not sure if that helps you or others, it worked for me!
Good Luck!