marine magic doser not working

[rocksteveo]

so i have a 2 week old marine magic 3 pump doser and it was working great for the first 2 weeks then pump A started making grinding noises and not pumping at all. so i replaced the motor with the extra one given and same problem, the i swithced the white front peice and still same problem. i checked the lines to see if there was a clogg or something and nothin. not sure whats going on here and im lost at the moment, any help would be great thanks in advance steve