I'm building a file provider extension and running into an issue I don't understand and am not sure how to resolve. I have been building the extension for a while and testing various things, and one of the biggest problems has been reliability. The current problem I'm running into is that when I build a new version of the process that contains the extension in Xcode, I get the error mentioned in the title when I try to register a domain (and the extension does not run). There's not much information I can find about what this error means or how to deal with it. I cannot find any running processes associated with my host application or the extension's name or id (though I may not have looked in the right places). Restarting the computer doesn't seem to resolve the issue either. Any ideas? (As an aside, at various points things have seemed to work just fine for me and even in a VM and then failed to work on other people's machines with no easily discernible reason, so any suggestions about ways to debug file provider issues are welcome)