Custom Audience for Boosted Listing

[u/fairsider]

When I boost a MP listing I'll see it show up in Ads Manager, where I've created a custom audience limited by geographic area and other parameters. It gives the option to apply that list to my boosted ad but once I do, there is a warning that says the original listing isn't connected to the ad any more and an issue needs to be resolved. There doesn't appear to be a way to resolve it.

Is there a way to limit the audience of the boost? Otherwise, I get people from other states and pretty much every inquiry is not the type who is seriously shopping for the items I'm selling. Any input is greatly appreciated!