There is too much pressure in the group head due to one of the following.

1. The coffee is too fine and the water cannot push through.
2. The dose is too high – ensure the dose in the filter holder does not rise above the lines on the side of the filter basket.
3. There may be coffee grounds stuck in the hole at the bottom of the filter holder. Remove the filter plate inside the basket and remove the basket from the filter holder and rinse clean under running water ensuring all the holes are clear.