I think it was really 2ppm to begin with but 4 cap fulls of prime really messed up the test.
When doing a fishless cycle you want to keep ammonia dosed up to 4ppm whenever it drops to 1ppm. In order for the cycle to continue advancing you need to keep ammonia at 4ppm. If you go down to 1ppm ammonia and let it rest there your BB won't continue to build up to higher levels as it will at 4ppm. Fishless cycling often takes a longer time than expected. If you finally beginning to see nitrites just keep dosing ammonia to 4ppm until the day you can dose that amount and within 24 hours there is no ammonia or nitrite readings and all you have are nitrate readings.
If you haven't read this AA sticky article you might find it quite helpful.... The (almost) Complete Guide and FAQ to Fishless Cycling - Aquarium Advice
Cycling won't happen overnight and it can often take a lot longer than what is expected. Yes, only dosing up to 2ppm will cycle faster simply because not as much bacteria needs to grow thus quickening the cycle. A lot of bacteria needs to grow in order to process 4ppm of ammonia. It would have happened, trust me I've been in the hobby since the 70's. And if you think the ammonia cycle is long the nitrite cycle is usually the longest.
If you start showing nitrites at a 2ppm ammonia dosing this just proves bacteria was building up in the time you were dosing 4ppm. It just hadn't built up enough yet. Patience is the key to fishless cycling.
Take it back up to 2ppm hopefully it'll drop tomorrow again than we will go to 3ppm