Remote control: WaitforConnectFaled


I am not an expert and I need help for the next.
I have two smartphones associated with my account, I can remotely control one but not the other (which I could before upgrading Host on that smartphone). The message I get says:

"No connection with partner!
The partner did not connect to the router.
Error Code: WaitforConnectFaled "

However the smartphone appears as online. What's wrong? Thanks for your help.