At first, make sure that your battery has juice left. If needed, replace the 9V battery inside the grip.
Check if the battery has been placed correctly, matching positive and negative terminals. If they are matched correctly, then the terminals might not be making proper contact with the battery. You will need to carefully bend the terminals to better fit the battery.
Geo3 is powered on, but is not firing when the trigger is pulled.
First, make sure your tank has sufficient air. Then check that the POPS on/off is fully engaged. If the POPS is engaged, be sure that the SFR is not set too low or flow is not blocked. Then try screwing the inline regular, where you adjust velocity, in or out to make sure it is not blocking air flow. Finally, if it is still not getting air into the marker, you might have debris inside the marker or damaged internals. Disassemble the marker and clean and check for damage.
Make sure your hopper has paint loaded and the paint is feeding into the breech.
First, make sure the "Training Mode" is disabled. If that does not work, there may be other settings that need to be set.
If the paint is in the breech, but the eye icon on the screen does not have a ball in it, then the eyes are not detecting a paintball. First, clean the breech superficially. If they are still not detecting, you will need to remove the eye covers and remove any debris from the eyes. If they are still not detecting, make sure the eye wire is not damaged. If damaged, new eyes can be purchased here and replaced.
At this point, air is being fed into the marker and the trigger is being detected, but it is still not firing. This could be a problem with the solenoid. Disassemble the marker and check the o-rings and gaskets for the solenoid. If the internals of the solenoid are damaged, it will have to be removed and replaced. A new one can be purchased here.
The unavoidable air leak... Don't fret, you can fix it.
First, make sure the back cap is secured. Next, remove the bolt and replace, clean and lubricate o-rings on the Prop shaft and Bolt Can.
First, check the inline regulator output pressure and the velocity to make sure the solenoid is not being over-pressurized. Then check if the 3 solenoid gaskets are intact. If damaged, you can purchase new ones here and replace them yourself. Next, check if the solenoid valve is damaged and needs to be replaced. If none of these stop the leak, and you can confirm that the leak comes from the solenoid, the internals of the solenoid may be damaged and the entire solenoid should be replaced.
First make sure the velocity screw on the bottom is not fully screwed in or out. Next, replace the internal o-rings and valves in the in the regulator.