Test readings:
Ammonia levels: 0.5ppm-0.25ppm
Nitrate levels: 0-0.5ppm
Nitrite levels: usually 0-0.5ppm
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Information quickly copied above.
For OP, one other would be to check ph. Below a ph of 6.5 the nitrifying bacterial activity will slow down.
Next one to check would be what water conditioner is being added(?) and if added to the correct dose. Possible that over-dosing may slow down the process.
Next would be what level of ammonia are you dosing to? What ammonia source are you adding and if the test kit is correct. Most fishless-cycling guides will suggest dosing to 2 or 4 ppm ammonia.
Would be handy if you can post further details on how you have been cycling the tank?