I learned long ago that just becuase you howl and you sound like a coyote, DOES NOT MEAN THAT THEY WILL ANSWER YOU! Using the howler is much more than just locating. For all you know, you may have howled, and a coyote, or two, headed your way to check out the new comer, but the new comer got in his truck and drove off[] Now the coyotes could start to associate that particular howl to danger! It is fun to drive the roads, at night, stop every now and then and howl, just to see if you can get a responce, but I'd suggest not doing that in the area that you plan to call in, especailly if you plan on using that particular howler. Instead, go into your area, set up to call, and start with your howler, howl two or three times, then sit for about 5 minutes, and if no one shows up, start using your rabbit squeels, Now, if there is a coyote in the area, and he hears a new comer, he may be interested and may even come before you start rabbit squeels, but if you don't see one coming and start rabbit blues, then he will think the new comer just caught a snack and will most likely want to come and steal/share it with you.
I'd say I get a vocal responce to my howls maybe 1 in 5 sets when I start with a lone howl, and if I get a responce, I almost always call in at least one coyote, but I have had many a time when I started with a howl and either didn't need any distress sounds before they showed or they showed up soon after starting distress sounds.
So no reponse is normal, but don't be fooled into thinking that if they don't answer that they aren't around.