To troubleshoot the fingerprint related issues, see: https://127.0.0.1:8442/api/v1/fingerprint/capture. Open the URL while you are presenting your finger on the reader.
The following fields are included in the output:
captureStatus: Can be 'Ok', 'Timeout', 'Error', 'NoReader'.
Width, Height: Fingerprint image size (in pixels).
Dpi: Dots per inch (used on matching side).
BitsPerPixel: Bits per pixel (usually 8 bits).
BytesPerLine: Bytes per one line in image (include align).
Image: Fingerprint image encoded using base-64 in gray scale.
An example of a sample output: {"BitsPerPixel":8,"BytesPerLine":256,"Dpi":508,"Height":360,"Image":"<fingerprintdata>","Width":256,"captureStatus":"Ok"}.