Trimmer Won't Start

I have a Troybilt 32CC trimmer. It didn't seem to be developing full power so I ordered a carb adjustment tool and tried tweaking it but didn't get any improvement. I tried closing the valves and opening them back up and then the darn thing wouldn't even fire! (I was using a drill starter.) I decided it was probably a carb issue and ordered a new one from Amazon. I thought I was getting a Walbro but it was actually a knock-off. I just put the new carb on and changed the fuel lines. It not only won't start, it won't even fire! I checked the fire with a tester and it's getting fire. It's also getting fuel through the carb. I checked the air filter and it could stand to be washed out but it's not oily or clogged. The only other thing I can think of is the exhaust screen, which is not easy to get too. I didn't change the gas but it was running on it a couple of weeks ago. Any suggestions? (I was already considering getting a new one but decided to try a new carb. One thing about the carb - I ordered it through Amazon from a seller called Fitbest. I gather they sell knock-off carbs and other equipment.)

 

A lot of cheap carbs are knockoffs. Is the spark plug wet? How much compression does it have? Try it witht he throttle wide open and no choke and see if it ever gives a sign of starting.