My rules when I did online dating were my age and up to 5 years older (although my boyfriend now is younger).
I wouldn't date anyone who specified a maximum age that was lower than their own age or where their upper end cut off was their own age. Even if I fell into that age range.
Willing do you know why people are suggesting your age might be the issue?
You seem to have some good boxes ticked so reasons i've rejected otherwise seemingly ok men are:
Arrogance - some women like it, I don't
A 'wandering eye' - checking out all women
No hobbies or hobbies that are incompatible with me and my life
Poor personal, including dental, hygiene
Men who are 'adoring' - the sort who you catch just staring at you when you are out at the pub quiz with some mates rather than joining in and having a laugh
Men who pass judgement on what I wear, what I drink or any other aspect of myself
Men who have an idea of what a 'woman' should be and expect me to behave accordingly...
Men who express racist, sexist, homophobic attitudes on any level - always pick them up on it and it's not popular!
Men who find an opportunity to make every conversation sexual.