So you did not add any ammonia after the 80% water change?
If thats the case, then its a likely scenario that you had overdosed on ammonia if its at 2ppm now after the wtar change, meaning that you had roughly 10ppm ammonia. That would very likely be the reason why the cycle has stopped.
Too much ammonia will overwhelm the bacs, hence why we need to be sure of how much ammonia we add to the tanks when we do a water change.
Hmm, i'd do another large water change, to be certain your water params have reset. At least its only a 5 gal tank, easy to do.
In fact when you calculate your ammonia dosages, using the forum calculator, bearing in mind to ensure the ammonia strength is correct, 1ppm desired ammonia level, 4 gallons of water volume ( this is after deducting @ 15% for substrate, plants and decor) you will have a more accurate idea of how much ammonia you should be adding for your stages when ready for ammonia full doses.