It could be a number of things....
If you have a manual, follow the trouble shooting tips in that..
The manual should be found at
www.wdp.tv but their website is bloody useless.
Open the breach and make sure the gun is clean around the bolt. Look in the ram slot and make sure there is not a build up of crap in there.
Make sure your battery is charged.
Make sure your dwell is at 14
MAke sure your LPR is around 95.
I hope that helps.
John