Here is a link to a website with photos of O. fragilis in flower and some more general information and more links to source with more detail. They also quote E. Ribbens who is mentioned and linked to by Justin above.
https://www.opuntiads.com/opun...
I live in the desert so cannot really provide you with any specific reasons why your plant is not flowering. Sounds like it might be a plant that rarely flowers to begin with, which probably means that it is finicky about the conditions for flowering to occur, so it may be good at surviving your climate, but it may require specific conditions for flowering to occur.
Anything else I can come up with would be even deeper into the realm of speculation. Where I live, the more I pamper my opuntias the less they flower, but what constitutes pampering in my climate is probably completely different in yours.
