Occasionally a customer has bad luck with a sourdough starter, it just sits there and does nothing, or goes mouldy. We send instructions with the starter, and have put them online and we have an FAQ (Frequently Asked Questions) page but it only needs one thing to go wrong, incorrect flour, temperature or contamination and it won't get started.
One such customer, Helen from Chichester purchased our Starter by Post and ran into problems, sounding slightly sheepish on the phone that it could have been customer error, but of course we never believe that do we. :) It was looking sad, the colour gives it away.
We had a chat about how it could have gone wrong and sent a replacement asking to try again after closely following the instructions, primarily to use a sterile container, warm water and good quality bread flour. She pinged us a day or so later and sure enough she has a healthy starter.
We've sent many hundreds of starters in various kits over the last six months but very occasionally, maybe a handful of times we've had to work with the customer to see what went wrong. Usually it is 'customer error', but we all started learning at some point so I'm happy to help if you're struggling.