If it is new as in brand new take it to a GXi Power equipment dealer and get them to sort it out.
https://www.gxioutdoorpower.com/
Good luck finding one.
Put a spannar on it yourself & they will void the warranty
If it is just a new to you mower, and you are not trying to start it with a control in the wrong place ( double check the PTO switch )
Then turn the mower on and off in a very quiet place.
You should be able to hear & feel the fuel solenoid on the carb turning on & off.
If some one else is handy touch the solenoid when the switch is turned on & off, you can feel it firing.
Nothing happens then either there is no power ( that includes a ground ) to the ignition switch or the switch is deceased.
These are Chinese made, knock down units reassembled in the USA to avoid import taxes and to pretend they are American made.
There is no service information available for any of the things GXi import and there are no parts breakdowns available either.
This is common for Chinese throw away stuff because writing a parts book cost too much money let alone maintaining a full service & parts regeime which is why quality equipment has a higher price.
The cheapest thing is to pump them out like saussages pack em into containers and ship them to the shops.
Slease bag importers just buy 20% + more of them to pirate parts from till the original is out of warranty then it is tough titties if something breaks.
FWIW a local importer of World Lawn self propelled told me to ship the broken cable to them so they could match it to the replacement.