Hi,
It’s possible they are both females. Females are the ones that just chirp and tweet. If the “male” never sang at all in a year, then there’s a good chance it’s a female. Makes sing to attract and impress a mate. A solo male tends to sing a lot because he is hoping to attract a mate. Of course, he needs to be happy and on a good diet. If he’s just eating seeds and doesn’t have any enrichment – toys, treats, greens, veggies, even dried mealworms or other insects – he might not be happy or have enough nourishment to get hormonal and want a mate. Since these birds aren’t showing much interest in each other, it’s another sign of having 2 females. I would separate them where the cages are apart, and see if this gets him to sing to get her attention. Also, try to locate a canary breeder and ask for advice on a good song food and how to encourage singing. There are breeders who breed canaries for shows, and they specialize in good singers so they can give you some tips. I’m sure you can find a group or page on social media.
Thank you for asking Lafeber,
Brenda