Please shake pen for 30s or at least till the steel ball inside is heard moving and a bit longer then Press the nib a few times in and out. Then hold down the nib. The ink will start to flow. After enough ink is on the top only press when you need more ink.
When you press the valve open to release ink. If you press too frequently then the nib will drench in ink and cause dabbing Some times you may need to dip the nib in cold water water or warm water to unblock the pores in the nib and release the valve to allow free flow of ink.Please try the above.
This should almost most certainly resolve any issues you may have .
GROUT REFILL
50 ml equal 10 refills in standard grout pen.