Unity Attach to Personal External Library Follow

I have an external library which builds to a DLL and is loaded from unity.  I keep this solution open in a separate window from my Unity project.  I generate the DLL and MDB and copy them into my Unity projects Assets/Plugins.

When i attach to the unity editor from my external libary, Rider says it's attached but all breakpoints I try to set state: "Not found loaded method for..."

Is there a specific configuration I need to get htis to work?  Works fine in Visual Studio for Mac.

Thanks,

Adam