Search not working for me on your forums

I dont understand the search function on your forum.
There are two search boxes one near the top then another on the top of the forum.

But the real issues are that it does not work. I looked up MBR once it found some things.
Then went back to see what other things are listed for this topic and it says Sorry - no matches. Please try some different terms. But there are!!!
If fact I tried to search literally on a topic I could see listed MBR to GPT and it said it did not exist! Even though I was looking at it.
So I'm very confused. Can you tell me what Im doing wrong ?? Why did it work once then ever again, despite there being posts of on that topic.

Regards