In the years that I've been traveling, I've noticed that there are a couple distinct slow periods in the year for opportunities: end of summer, and winter holiday time.
At the end of summer, people are trying to get their vacations in before kids have to go back to school. This means decision makers are either not around, or they're just trying to fill in temporary gaps in staffing with their PRN employees to cover a few extra shifts. You might be able to find local contract work during this time through an agency like Maxim or Social Work PRN. But those 13, 26, and even longer travel contracts - those probably won't be around just now. It'll pick up right after Labor Day.
The other slow period I've noticed: Thanksgiving through mid/end of January. Truthfully, it's the same reason. Contract travelers have to go through not only their agency's onboarding processes, but they have to go through the hospital's onboarding process. This means that even if a decision-maker (department manager) has gone through the steps of phone interviewing you and they want you to start, everyone is relying on the people at the hospital, and at the agency, who actually process your paperwork, get you to your urgent care clinic for bloodwork and labwork, to all be around during the longest holiday season of the year. It's a lot to bank on.
Additionally, if a traveler is brought on during this time frame, there has to be someone to orient you (either official hospital orientation, or just someone to train and shadow with), and staffing is generally low due to people being on vacation. It's more likely that you'll start to see more responses come the end of January, when managers are little more relaxed, and the permanent staff are back from their vacations.
That's not to say that travelers never get brought on during these periods: they do, but the availability of jobs is generally far less than what you'll see the rest of the year. If you're out there looking, I say you should still apply, but know that it could take a little bit for a hospital to make a decision (even if the job is actively posted).