Moss rose refuses to flower

This is the second time I have tried to grow moss rose, but it never flowered. It look like buds are forming, but they are not flowering. The plant looks healthy. The nearby calendulla is flowering nicely, and cornflower also just opened the first flower.

Any suggestions? Thank you.

How old is the plant?
It usually takes around 50 days for flowers to start appearing but make sure to keep them in extra sunlight as well, as they appreciate it a lot.