Certain techniques only become available after gaining key techniques, but it sounds as if you knew that.

Volley Shot is a pretty hard tech to get as far as I know, at least before LV30 ...

Try Tech Find, I've never used it myself or ..just try and get lucky. Exhibition games vs. teams with the volley shot technique are usually useful.

About the error, this is something I don't think is explained in the tutorial or anywhere else. The "Techfind!" flashes red and blue, and usually if I hit "X" when it's red, I fail for what I thought was no reason, but when it's blue I usually gain the tech 99% of the time, and if I don't I get an error, e.g. "Bob's level is too low!"

Try hitting X when the "Techfind!" flashes blue, that should work.