Hello riverflower, the net is a really excellent idea, as it prevents them from digging up the roots and ensures more effective regrowth.
When growing from seed, there are so many factors that can prevent the seeds from germinating. Often it's because the soil is too rich and the seeds prefer nutrient-poor soil. Some seeds don't like moisture, only wetness, while others don't like to be planted alone and thrive when sown together in a pot and then pricked out.
It's really a matter of constant trial and error and research.

!PIZZA