The resin system is curing too fast in the bucket before it can be applied to the roof.

Either too much catalyst is going into the base resin causing it to rapidly cure or the wrong catalyst is being used.

Always check the catalyst guide to make sure you are putting the right amount into the resin, Get an ambient temperature reading and for extra accuracy use a digital thermometer to check the resin temperature.

Only mix between 2.5 and 5 litres of base resin at any one time and before you start the roof, perform a small test by applying catalysed base resin to an off cut of OSB3. This will indicate how much working time you have with the resin before it starts to cure.