Ok have the facility turned on so I am watching the post I have made a comment on & receive an email when a new post has been made
But when I have clicked on aid link I get this You are not authorised to read this forum.
When go to forums I can still read the said post why 
Educate me- why do you need an email when you post on here?
It send me an e mail when somebody has replied to a post I have made a comment on also take me straight to that post so dont have to read or scroll down to it
Can make things easier that all
Are you set to log in automatically or do you log in each time you visit?
Automatically log in in to site only just started happening sometimes
That’s me out of suggestions then. 
It maybe that you have a corrupt cookie that fails when a new window opens, try deleting the cookies relating to TruckNet while logged out of the website, then Log in again and see if a new cookie makes any difference