I'm certain the Toxivec worked to some degree but that would only be temporary. It is quite possible that you could be having a nitrite spike without signs of ammonia. Nitrites are just as toxic and it takes just as long for the bacteria that consume nitrites to become efficient as it does for the bacteria that consume ammonia.
Having said that, give the aro some time. If it nibbled, that's a good sign. Don't force the issue. Try again tomorrow.
Having said that, give the aro some time. If it nibbled, that's a good sign. Don't force the issue. Try again tomorrow.