@Matthew Vernam.
Before considering a termination you should look into the following...you can then decide what to do depending on what you find.
1) I would encourage you to look at where your property is being advertised...at a minimum you should be able to find it on sites like Zillow, Realtor.com, HotPads, etc. If it is not on there your property manager isn't doing their job maximizing exposure. You should also encourage your PM to advertise on Facebook.
2) Look at your ad and see if there is something missing. Is the ad description lacking...does it include enough detail? Are there any selling points missing? Are the pictures high quality? You can get professional pictures for as little as $200.
3) Look at the "views" or "saves" your ad is getting on Zillow or other sites from prospective renters. Then compare that data against similar rentals in the market. If your rental is getting significantly less interest than your competition, it is probably priced too high. A good property manager would be tracking all of this and guiding you on any price adjustments that might be needed.
If your PM is failing you on each of these items, I would call them out on it and start looking for someone else if they don't respond accordingly.
Good luck!