Gun trigger problems

I have a wire matric 255 and I have a magnum pro 250L gun, when I plug the gun in it runs the wire without pressing the trigger. I turn it off and back on and
it stops driving the wire but trigger still doesn't work. Any ideas??
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.