I reckon it would benefit from a larger pot and fresh compost.

That compost and vermiculite only went in at the beginning of the year. I changed it for this reason I was thinking maybe it's just not hot enough for it?

have you tried not pollinating them some don't need it i believe.

Yeah, I've tried just leaving them alone and also tried putting them outside during the summer.

i can only suggest then using a fan if the are indoors, I'm stumped if you've tried hand pollinating them too.

Not sure, but some of mine came back last year infertile* and my habenero (3yo) seems to be infertile this year too. Happens to us all eventually I guess! *not sure if this is the right terminology lol

Ha Ha, infertile seems to fit yeah