A Ceremony of Losses
It's kind of a idiotic concept, the Andorian people have been around for multiple thousands of years with four genders, and suddenly that's one of the prime reasons they're now going extinct?
There could have been some kind of radiation burst that affected them, or a mutated STI, or any kind of medical incident that has affected their biology which has only gotten worse over time.
established that the Andorian reproductive crisis was ultimately caused by a mutation the species underwent thousands of years ago that gradually began causing more and more miscarriages and stillbirths.
And, no, there's nothing implausible about the idea of reproductive difficulties gradually causing a species to go extinct. Just check out the difficulties scientists have been having getting the panda species to reproduce.