A Connection could not be established, while team viewer is running on partner computer


Kindly help to advice. Very much appreciated.

I can access to my partner computer, but not alwyas. Even my partner computer is on (and team viewer is automatically on, as it is set to start with window).

But when i key in the password preset, I see the message as below :

"A Connection could not be established. Team viewer is not running on partner computer"

Thanks for your advice in advance.