You dont have the proper angle and probably not pixel density. Additionally, at night your camera will not be able to read the plate because of ir reflection. You need to dedicate a camera to lpr. See lpr section. If you cant read the plate, the software cant.
In addition to having the proper camera setup, (see LPR threads) there seems to be some voodoo/magic involved in setting up BI to use the platerecognizer function. It apparently only sends the 'alert image' to the cloud API, so you need to dial in your trigger settings such that he 'alert image' is most likely to have a plate in it. I find this non-trivial, given the various speeds at which cars move through the scene. Also, tho I have enabled the feature for one of my cams, the web site has yet to show any API calls having been made, tho some of my alert images do actually have plates in them. The BI documentation around this feature is rather sparse... Can anyone who's made this work clarify how to get BI (v 5.0.5.8) to send images to the API? thanx.
Edit: turns out i had misconfigured the country/state field in the BI/trigger config. I had "US/CA" but it want's "US-CA". It was failing SILENTLY to contact the cloud API until I corrected that...