Humm this should be a simple problem but i dunno sometimes weird things happend to spyders...
Ok ima gunna give you a list of things to do if you follow them right it should get your sons spyder back in working order.
1. Take all internals out of you gun (striker, bolt, etc)
2. Unscrew the ASA (place were your tank goes), well take the screws off
3. now take off the trigger frame (only two screws but be sure not to loose the wasers because in some cases if you do lose the washers you will have problems with the striker attacking the screws when they are fastened into the gun tightly)
4. Now that everything is out you should have all of this stuff lying outside of your marker. (Bolt, Striker, Striker buffer, Spring, Spring Guide, Velocity Adjuster, pin for Velocity Adjuster, small Disks that go inside Velocity Adjuster, trigger frame, screws for frame and ASA)
5. Now put the bolt and striker back together and put them into the marker (make sure that the front end of the striker (the part with the o-ring) is facing foward toward the valve assembily)
6. If you want u can put the striker buff back into the marker. Althoguh it realy isnt an important part to the gun, but you can put it in if you feel like it.
7. Now put the disk into the Velocity Adjust
8. Put the spring into the striker(already inside the marker), then put the spring guide into the spring.
9. Put the Velocity adjuster in the marker and secure it with the Velocity Adjuster pin
10. Lastly put the trigger frame on and besure you did not loose any of the washers lol. then put you ASA back on.
Now your free to air it up is should fire and recock fine... if not you can E-mail me at firstname.lastname@example.org
or AIM me at thechubbss12