@mattdjuk This could be something (clutching at straws a bit here)...
I was just looking in the cookies, I see these:
Screenshot 2022-05-26 113221.png
It has 2 express.sid cookies
1 is for forum.$$$$$$$.co.uk and the other is for .$$$$$$$.co.uk
@baris thank you for your reply.not only user,but also administrator, when I check the ajaxify.data.topics on console, that topic has no tid and the array's length is 2.It's werid that I can see the topic on that page only when I login with user account.I cannot see it when I login with administrator