How do you PM others ?
Don't bump five year old threads to post completely unrelated content.
Click on the conversation bubble icon on the semi-transparent bar and then click on the plus button. Alternatively, go to your intended recipient's profile, click the user button (to the right of their username) and then Create Conversation.
Or leave a message on their profile asking them to dm you? That might be a better, nicer way than a direct pm. Just a consideration.