Never give up! I have to say right off the bat that I am always seeing large guys -- be they a bit [or a lot] chubby or simply big and tall men -- being cruised in bars [especially bear bars], so I know there are plenty of admirers for larger men. And yes, even older larger men.
Be upfront about your size on any web sites. Some guys are positively turned on by large men. I used to be a lot heavier than I am now and I was always amazed at the guys who seemed to be turned on by my sheer bulk or by my belly. [When I lost weight I used to joke that I'll lose all my boyfriends, but luckily that didn't happen. There's someone for every size!]
If you lie and say that you're thin or small or what-have-you, the truth will come out when you meet face to face, so what's the point? As I say, I believe there are enough men who are into big guys of any age that there will hopefully be men who are interested.Check your profile and see if there are any other things that might be a problem. While honesty is always the best policy, you don't have to tell them everything!
I find that big men are much admired in the bear community. Even if you're not a hairy, bearded bear type, you can still find admirers. [If hairy guys are a turn-off to you, I can also tell you that many bear sites also have smooth-skinned men on them].
You might have tried some of these sites already:
BiggerCity, the web site for gay chubby men and their admirers. And there are similar sites if you google.
Silver Daddies for older men and the men who admire them. Recommended. Lots of older guys, big guys, chubby guys etc. Something for every taste.
Bearwww.com for bears and bear admirers of all ages, types and sizes.
Bear411 Ditto. As I say, big men are appreciated in bear culture.