Where did you get the kit from? if it was Moorlands (www.cheesemaking.co.uk), speak to Katherin, she’s very helpful. How long have you had it? Check the use by on your rennet, it’s not usually very long (we get about 3 months on a 25l drum of Danisco Marzyme), same for your starter cultures unless you’ve kept them frozen, even if freeze dried they can still be less effective and you end up with a slow vat. What type of cheese are you trying to make? A hard (Cheddar/Derby) or soft (Capricorn/Camembert) type?
The kit will be fine it uses the same ingredients as we use for making cheese on a large scale (unlike home brew beer and wine kits), although don’t expect your first attempt to turn out fantastically, it takes practice. Don’t rush it either.
We never add any Calcium Chloride to help set our Goats Cheeses (all pasteurised) for what it’s worth.