I had the same issue with mine fresh out of the box. Racked the bolt once, dry fired. Second time, nothing. Dead trigger. Couldn't even get the trigger to engage so I could dry fire it to disassemble. Eventually got it it by racking the bolt hard and letting it slam shut while holding the rifle at different angles lol.
Contacted wolverine and although sending it back was an option, Dave explained the process and it is an easy fix and I wanted to try it myself first.
Two things you can do -
First, theres a little flat spring at the coming up from the bottom rear of the receiver. Hook it with something (I just looped around it with a piece of string) and bend it upwards. This will increase the spring tension on the sear. After this I had a bit better results, actually got the rifle to fire, but the gremlin would reappear after one or two rounds.
So if bending the spring isn't enough, the issue usually is the little bit of play between the sear and the pin that holds it in. Apparently since they were formerly full auto receivers and have a few select parts missing, the space left over causes the problem.
I went to home hardware and found the smallest washer I could find, they actually gave it to me for free from the package since I only needed one, unfortunately I don't have the package with the size. Just bring in the pin and find one that fits. Went home and having minimal tools in my temporary apartment just spent 20 minutes sanding it down with my finger lol
Got it to fit and took it out the next day, haven't had an issue since.
There is a good YouTube video outlining this process. I'll see if I can find it and post a link.