Scan gear is not detecting our IR3300, how can I

Make sure to use the B&W version of ScanGear not the Colour one.
Latest version I think is v2.21. See http://www.usa.canon.com/html/download/canonnetutils.html
Also make sure your copier has an IP address in the same IP range e.g. 192.168.0.x (where the first three numbers out of 4 are the same) as your computer.
Also turn scanning online at the copier using the instructions in the manual included with the download. Be sure to turn scanning off so that other functions can be used when finished.
You may wish to try disabling a firewall (temporarily) or a direct connection to the copier if you still can't get it to work.