Have a 2020 800 trail
When you turn the key it sounds normal, When you go to turn the key to start it will not do anything. I have replaced the started solenoid and few weeks ago I bought a couple starter relays the bigger and the smaller ones. As soon as I replaced the bigger starter relay last week it started drove it around then sat for about week. My wife went out and started it up and she used it to pull out a stuck rider mower. went she may of ran it for 10 min. Came and parked it. Next day went to start it and it started doing the same thing again.You it will start with a screw driver on the solenoid.I just opened the battery cover other day and the POS, Cable was full of corrosion so I went and got one made and have another one coming it the mail. This thing has me puzzled! Next step I was going to replace the ignition key next possible.If anyone would have a suggestion it would really be appreciated. Thank You ALL have a wonderfully night!

[2015 Z Force 800 53/Trail EPS]

It is common for the key switch to go bad, but it is also common for the gear selector switch to go bad as well...and when it does. the interlock relays don't get the ground it needs to send power to the starter system. Either the neutral or park light has to be on or if in any other gear position the brake lights have to be on..so the next time it has no starter, put it in H or L and hold the brake on enough that the brake lights are on and try it. If it starts, then see if when you are in N or P if the dash lights are on. IF they are, look to those relays. IF it still won't start on H or L with the brake on, test the key switch. Also, the kill switch is known to get corroded terminals inside...and it can do the same thing. Work it a few times and try it. 

Hello, 2021 800 ex owner here and I have a similar problem, but mine seems to only occur in cold temperatures around 40 deg  and below. Once it starts its good for the day. Have not had any start problems since temps have warmed up. Very strange.

[2015 Z Force 800 53/Trail EPS]

Hello, 2021 800 ex owner here and I have a similar problem, but mine seems to only occur in cold temperatures around 40 deg  and below. Once it starts its good for the day. Have not had any start problems since temps have warmed up. Very strange.

It is common for a contaminated air temp sensor to effect the pulse width the ECU sends to the injectors especially during cold starts. That would be the first thing I would pull and clean. The next thing is the idle air control valve. It may need cleaning or replacement. The next is the TPS or Throttle Position Sensor. After you shut it off never touch the throttle while starting as it will conflict with the last stored data sets. They also fail but its a bit more rare. The last thing is system power. If your battery isn't up to snuff, during cold cranking the system power may fall below 12 volts and when it does the coil can't charge enough..as in create the field necessary to generate a spark when the field collapse during firing. Have the battery load tested.

It is common for the key switch to go bad, but it is also common for the gear selector switch to go bad as well...and when it does. the interlock relays don't get the ground it needs to send power to the starter system. Either the neutral or park light has to be on or if in any other gear position the brake lights have to be on..so the next time it has no starter, put it in H or L and hold the brake on enough that the brake lights are on and try it. If it starts, then see if when you are in N or P if the dash lights are on. IF they are, look to those relays. IF it still won't start on H or L with the brake on, test the key switch. Also, the kill switch is known to get corroded terminals inside...and it can do the same thing. Work it a few times and try it.

Your knowledge of these machines and how they work is truly impressive, as is your willingness to help and share information. 

[2015 Z Force 800 53/Trail EPS]

Thanks, just trying to help where I can.

As a clarification my no start issue is the same as the original poster. Turn key to run and everything is normal, turn key to start and nothing happens, no solenoid click or anything. After repeated tries, moving shifter to neutral, park, etc it eventually will  crank and start. It will then start normally the rest of the day. Since temps have warmed it starts normally every time. Coincidence?