Could you post a picture of her?
Also do you provide oystershell for her?
Vent checking is usually the best way to determine sex when they’re little but it isn’t 100% accurate, blood tests are the only sure way to tell.
The best thing would to have her get checked out by a vet to make sure she isn’t internally laying if she is a she. Symptoms can be subtle at first, or so I’ve heard. Once more obvious symptoms appear prognosis is poor.
Have you seen her behaving in a broody manner, making nests ever? Males will do this too so it isn’t an indicator of sex, but does show if he or she is feeling more hormonal.
Other than issues like salpingitis, tumors, oviduct impaction there aren’t many reasons why she wouldn’t be laying that I can think of. Usually you will see signs of illness unless it’s in the very early stages when symptoms are more subtle.
In chickens there’s a condition called false layer syndrome, it’s when a female chick contracts a coronavirus called infectious bronchitis virus at an early age which causes inflammation of the reproductive organs and as a result they never develop and thus you have a hen that just never lays or has serious reproductive disorders.
I haven’t found any clear information on whether geese can catch that virus and if so if it causes the same issues in them but if all else it’s a possibility to explore.
Another possibility is that she’s a late bloomer, all of my girls have laid in their first years but 2 years old is technically when they’re truely mature, I’ve never owned Africans but some breeds lay more than others but larger Africans “super” lay less than smaller Africans according to Metzer, maybe she has those genes in her?
https://www.metzerfarms.com/compare-geese-breeds.html