Maybe it is just late blooming this year; mine only started into flower this last week. I thought it was dead earlier in the year, due to the last terrible winter & the subsequent drought here in the UK. It still isn't as prolific as it has been in previous years.
I've had a few blossoms, but nothing compared to last year. I haven't been feeding it as often either... I'd try some plant food. One of my favorite plants. I have to bring mine in for the winter, but I usually get a few blooms, so it is worth it!