I have a Mini-Famous Dark Blue Calibrachoa that was blooming well. The last couple of weeks it doesn't bloom at all, just have the green leaves hanging down.
Certified GKH Gardening Expert
If they're in a container or hanging basket, they normally require additional fertilizer. That said, the nitrogen content may be higher than it should which can limit the flowering. Phosphorus can help offset this. I would recommend adding a bit of bone meal to encourage more blooms. Here is more information: https://www.gardeningknowhow.com/ornamental/flowers/million-bells/calibrachoa-million-bells.htm