
One of my males alerts me by tasting the bitches wee about 7-10days before the season starts, I then start checking the girls with a tissue each morning before they have a wee, they tend to come into season within days of each other.
Entire males of any age can sire pups, there may not be as many sperm as when he was younger but you only need one sperm per egg for her to get pregnant, oldest sire in my breed I remember hearing about was 14yrs old.
The first season is Mother Natures way of saying the bitch is physically old enough to produce pups[in the wild she would have a phantom and produce milk for the alpha females pups whilst she goes out hunting], we wait till they are mentally mature before breeding from them. Is your girl mature physically, this happens earlier in smaller breeds[mine have been 8 months when they have their first, full sized but needing to fill out a bit] and much later in the bigger ones.
Be patient, it will happen eventually.