If it helps, try downloading both Libby and Hoopla. They have different titles available on each even when I'm signed in with the same library card. Or sometimes one will have the audiobook version while the other one doesn't. The method of checking things out is slightly different between them, too (Libby is the one with limited copies available and puts you on waiting lists for popular ones; Hoopla has everything available always but with a limit on how many you can check out every x days).

Apologies if I'm telling you stuff you already know. 🥲 But it might be helpful info for someone out there!