The fuel line or the fuel filter inside the fuel tank may be clogged. If that's the problem it may be an easy fix. The whole thing may be a single unit that could be replaced easily and inexpensive.

I've replaced the bad lines and you can see the fuel bubble in the tank when at idle, Wouldn't that signify that it is getting fuel? Would the spark arrester cause such a problem?

Sounds like it's not getting the fuel. It may be the diaphragm in the carburetor which works kind of like a fuel pump. It could be worn and stretched out. I just had this problem with my trimmer.
Now I have the opposite problem of yours. It will take the fuel but won't idle.

Could be a carb diaphram issue (pinhole or slight tear) also could be dirty carb and air filter or out of adjustment . Review Previous Threads on carb cleaning and adjustment . We have gone over these items numerous times . I have indicated to Ceezaah an effective carb tuning sequence that may well assist you . Ensure you have fresh gas good spark plug and treat the fuel with a concentrated cleaner treatment . Let us know how you make out . Depending on how old you trimmer is it may require a carb kit and overhaul .

One very stupid question. You said you squeeze the trigger and the engine is still at idle speed, you did not indicate that the engine is choking, you check the throttle cable is connected to the carb?

Just a stupid question to cover the basis!!!