I tried to home brew, boiled apples and used the extracted juices, 8.8 litres placed it in a bucket with a grommit added 5grams of champaign yeast, let it sit for 4 weeks but is still very flat how do I rectify this?
Did you take an hydrometer reading (OG) before ferment?
If so, what was it and:
- take another reading, has it go down?
- Has it finished? with champagne yeast it should go dry (depenging on your OG reading), so a reading about 1.000 means there are no sugars left to ferment
If you didn't take an hydrometer reading (and have a hydrometer) take a reading now, wait a couple more days and take another reading, did it then go down?
If you don't have a hydrometer... get one, they are about £3.00 GBP and take a reading
As you can see a hydrometer is essential in brewing and cheap. This is the best way to see if anything has 'happened' and will give you an ABV at the end for your final product.
As the other comment said, in primary fermentation it will be 'flat' once fermentation is complete or stopped, then the 'fizz' is either produced by a secondary ferment done in a pressure barrel or bottles OR forced carbonated with CO2.