LogFAQs > #970048174

So the way the suggested raids work, is it's not necessarily showing you a currently available raid. When you select one, it just searches to see if there's a matching raid being hosted somewhere (species, level, Tera type), and slots you in if it finds one. What this means is you can just sit there doing the search over and over and it will eventually get you one.

After reading about this, I refreshed until I found a Scarlet exclusive that I didn't have yet, and then sat there selecting it like 10-15+ times until it finally worked (I just had my Switch next to me while I was using the computer, tapping A every couple minutes). In this case, it was a 3* Oranguru, so I can see that not being a popular raid for people to host, but other things would hopefully take less attempts.