The VTEC spool valve assembly is #11 bolted on the back side of the head. Picture is a little goofy, that spool valve is actually over towards the distributor-end of the head. Check the plug on the VTEC oil pressure switch #14 - if that's loose/dirty/corroded or broken wires that can cause it. Also check the electrical connection to the VTEC solenoid on top of that assembly.
Sometimes the spool valve is sludged up.
If you feel comfortable doing this, unbolt the assembly from the head & clean out the screen in the gasket #13. Better yet, get a new gasket from a dealer because it'll probably be hardened with age & leak when you put it back together.