Q.Rosella Plants
I have two rosella plants almost two metres high. They have been flowering, the flowers are open in the morning and close up a few hours later. The next morning they are on the ground. I have opened up to see if I can see any insect. But nothing. However I have finally sprayed with season eco pest and even tried to net them so nothing at night could get them but nothing seems to work. More flowers appear but the same thing happens. Any thoughts on this please?

Certified GKH Gardening Expert
This is typical. Blooms will last from one to three days, at most. If they get pollinated by an insect, then they will close sooner. This article will help you with its care:
https://www.gardeningknowhow.com/ornamental/flowers/roselle/growing-roselle-plants.htm