Just keep at it. Always work on getting into stands without being seen or smelled. I start out soft in case there is a dog close by but loud isn't necessarily wrong. Coyotes all have their own personality and you never know what happened to them that morning or two weeks ago that shaped how they react. Many times I've sat a stand and glassed coyotes in 2 directions before I started calling, and when I started, one comes in as fast as he can get there while the other goes straight away at the same speed.
Good answeres put forth here but there's another possiblility. Coyotes usually come to a call for a free meal. In other words, they'r HUNGRY.
Those 2 may have spent the morning feeding on gophers, rodents, rabbits,
roadkill, etc. and already had a full belly in which case they most likely would run the other way.