Unsolicited PM's are against Forum policy. An agent has to request/allow you to PM them and then the option will appear on their profile when you open it. Check out https://forums.xfinity.com/t5/Getting-Started/Private-Messaging/m-p/3217923
Also, in our profile settings, there is an option to turn on private messenger. Click on your picture/icon in the upper right next to the notifications icon and select My Settings, then Preferences, the Private Messenger.
This is working as designed. Due to the influx of unsolicited private messages sent within this community, we have disabled this feature until you have posted your question on a public thread. I have verified that this feature is currently enabled with your profile. You can get specific directions on how to send or read your private messages here: https://forums.xfinity.com/t5/help/faqpage
As mentioned by @jav6joev sending unsolicited private messages to any user in this forum does violate forum guidelines (found here: https://forums.xfinity.com/t5/Guidelines/Xfinity-Forum-Guidelines/td-p/3115028) and Xfinity Forum Acceptable Use Policy (found here: https://forums.xfinity.com/t5/Guidelines/Xfinity-Forum-Acceptable-Use-Policy/td-p/2618379). We ask that you review those documents as violations could result in a revocation of your Xfinity Forum posting privileges.