Having the same issue, killed any active sessions but it doesn't change the message. On top of this, I have a 3 session upgrade (which I bought today because of my first session being stuck) and I've only used 1-2 sessions (depending on if the first one is still stuck) today, so there is no way that I am actually using Max Sessions. I should still have one left... sigh.
I'm also having the same issue. Started using my second key and it worked once - and then a plugin crashed it and now it says max sessions as well.