I just tried to activate Jetpack on a blog that a friend of mine operates, but for some reason I received the error message above as I tried to activate Jetpack. So, what did I have to do? I did some Googling, and luckily I found a solution, so now I have Jetpack up and running on the blog.
So, what can you do if you get the following error message as you try to activate Jetpack on your WordPress blog?
GnuTLS recv error (-9): A TLS packet with unexpected length was received.
I can not guarantee that this solution will solve the problem for you like it did for me, but hopefully it will. Just follow these steps, which I followed myself to get this working.
Download the WordPress plugin Core Control.
Activate Core Control.
Go to Tools – Core Control.
Check the box next to "HTTP Access Module."
Save and press the External HTTP access in the menu at the top.
Look for cUrl and Disable Transport.
Now you should try to activate Jetpack again.
This worked for me, and just to be nice I went back and reversed all my changes done with Core Control (I activate transport for cUrl and removed the check from HTTP Access Module). Then I disabled the plugin and everything is working great. Hope this has helped you as well!