Your ammonia level is too high. If the ammonia level goes above 4ppm the cycle will not occur. You only need 2-3 ppm of ammonia to cycle the aquarium.
Make sure the ammonia does not have any soaps/ surfactants in.
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Check your tap water for ammonia, nitrite & nitrate. If you have 20ppm of nitrate in the tank and it hasn't cycled, the nitrates are probably from the tap water.
Don't bother monitoring nitrate levels until the ammonia and nitrite levels have gone up and dropped back to 0. Then you can monitor the nitrates.
Nitrate test kits will read nitrite as nitrate and give you a false nitrate reading.
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The cycling process takes around 4-6 weeks.
The ammonia causes bacteria to grow in the filter and they eat the ammonia and convert it into nitrite.
When you start to get nitrite in the water, you get more bacteria growing in the filter and they eat the nitrite and convert it into nitrate. You get rid of nitrates with water changes.
When the ammonia and nitrite have gone up and come back down to 0, the nitrates start to go up and the tank is considered cycled.
If you tank has only been running for a week, you still have 3+ weeks to go