A couple of things to check:
Make sure the VCR is outputting video to the connector you are using. Some VCRs require selecting the output channel. Make sure a tape is playing to provide a usable signal.
If you are using a RCA to BNC converter, it should work fine.
Make sure you selected the configuration file with the appropriate input. If you select the S-Video input, the card will not see the signal on the BNC input. Make sure the signal format is also correct.
Bruce
Bruce Ammons
Ammons Engineering