I have mine against a north facing wall, never had any problems with flowering. I only know that any pruning needs to be done immediately at the end of flowering, any later and you lose the next crop of flowers. Could that be your problem?
Hope it does well for you this winter.

I bought it last winter, and after I planted it, all the others in the garden centre came in to bloom, whereas mine in the garden didn't.

So I do not know what is wrong.

If it fails to flower I may just pull it up, as it takes up a lot of room, which can be used for plants that will actually flower.

Thanks for your help.