Here's the thing.

I log into my account. Let's search for "yuri", for example. There are some thumbnails and I can select page 2, 3, 4 and others. All is fine for now.
Let's search for "yuri yaoi". There are thumbnails again, but no pages at all. I can still click on a thumbnail and shift through by pressing 'next' button, though.
Let's log off and search for "yuri yaoi" again. And the pages have returned.

I have repeated this behavior on the firefox 75.0 and the latest chromium without cookies.

There are only 35 images with both yuri and yaoi as tags. How many images do you have visible per page?

skylightcrystal said:

There are only 35 images with both yuri and yaoi as tags. How many images do you have visible per page?

20 for default. Changed it to 5 and still no pages.

p.s. works on any combination. "touhou hakurei_reimu", "2girls 1boy"...

I get pages when doing those searches but the page numbers are away to the right of the thumbnails instead of below them.

Fixed. This problem occurred when a Member-level user had the "Deleted post filter" option turned on and did a two tag search.