'08 Apex GT Ltx goes click click click but starts once......

[actionjack]

If you use a multimeter on the battery when you are trying to crank you can see if it is having significant voltage drop. I tried to revive a new battery for my ATV last fall and I could charge it up full but put the load of the starter on it and it would voltage significantly. New gel battery and voila good to go.

 

[Roadrider]

I agree, computers need to see about 10.5 volts
minimum while cranking. If the voltage drops below
that it won't fire. Easy enough to check.