My Echo trimmer would not start after sitting all winter with gas in it. Put fresh gas, still no start. I took out the spark plug and dipped in gas. Shook out the excess. Replaced, Fired right up.
You know it's a fuel related issue then. Check from the tank to the carb. Filter, fuel lines, does it have an impulse line?
I had a bear of a time with my old Ryobi gas trimmer. Then last year I bought a Stihl battery trimmer. No issues this year. Lol