[Jeepwm69]

Check your gear position switch plug. If any of those connections aren't getting a good connection, you won't get spark.

There is a wire that comes off the back of the motor, and runs up to a square grey plug under your right buttcheek when sitting on the seat. It's a PITA to get the plug apart, but that's where my problem was on an 07 420FM. Mine wouldn't start in 1st, and when I bypassed the plug with a jumper on the 1st gear specific wires, it would start in 1st.

Take the plug apart, clean the connections well, and see if that helps.

 

[Jeepwm69]

Hold the brake levers on handlebars when trying to crank. It should crank in gear with them held.

It won't if the gear position switch isn't working or the plug isn't making a good connection.

If the ECU can't tell what gear the machine is in, you get no spark.

 

[Jeepwm69]

Your new 500 is the same way. Interestingly enough, if it's started, it will continue to run.

420's are the same way.

My 09 intermittently doesn't show 3rd gear on the display. If it is in 3rd and 3 is not displayed, it will just turn over and not crank. If the 3 is showing on the display it will crank.

I'm sure it's a loose connection in the gear position switch plug, I just haven't messed with it yet.