Tag pages say “No matches found.”

Hello, I created few tags on admin and tagged some products. So tags are shown like this in product pages;

    Product Tags
    Other people marked this product with these tags:
    my tag(2), my tag2(5)

Each tag’s name is a link, so I expected tagged products are listed on the tag page when I clicked the tag name.

But the tag page says;

    Products tagged with ‘my tag’
    No matches found.

I have no idea why the page doesn’t show tagged products. I cleared cache in case the cache caused this, but nothing was changed.
Could someone help me please?

just got to index manager and re-index