when i convert PNG to EPS not converting, show images with black background only?

[vinwebdevelopers]

Hi, I am using this API to convert my PNG images to EPS, but not working returning black background images. My PNG Image: https://designasign.com/php-scripts/public/output/full/Vinyl_Lettering_1782714207.png

Please check here demo of the API: http://rest7.com/raster_to_vector

I need .eps image. When i download and check it appears like
https://designasign.com/php-scripts/public/output/svg/Vinyl_Lettering_1745323227.eps

Why it's not working? Please respond ASAP.

Thanks.