When I click on it I get the message: "The default setting for Threads I'm On is to display the 100 most recent replies. If you would like to change the setting to see more or fewer replies, please do feel free to customise your options. You can also customise how you sort Threads I'm On and how many days Threads I'm On checks back to." 
It was working til about a week ago! And I am On Threads!
I use Chrome on a PC.
Any ideas? I can see 'watched' threads, and 'threads I started'!