To you, you have checked everything: spark plug, ignition coil. But to me you have not checked everything. Try few more things:
Check if the air filter is clogged. Clean it.
Gas to oil ratio might be inappropiate
Fuel might be bad
There can be many reasons that your echo 490 chainsaw won't start. You have to look into these things to find out what is the issue your chainsaw is not starting:
Make sure you are not using the old fuel in your echo chainsaw
Probably the settings are wrong. ( Cold start is different and warm...