"No valid source or MP locations"
Based on your installation line: "C:\Windows\ccmsetup\ccmsetup.exe" /runservice /ignoreskipupgrade /config:MobileClient.tcf "
You are NOT explicitly defining a Management Point or Source. That's perfectly fine... if this client is joined to the domain, your company HAS extended the active directory schema for CM, and your CM infrastructure servers have rights to YourDomain/System/System Management container... so your environment can properly update the entries in that location.
You see, clients on that same domain, 'in general' will ask active directory "ok, so... what Management Point should I use?" Start there... the log to look at is SiteComp.log on your Server, you should see it referencing the System Management container.
If that all looks perfectly lovely... my next guess is boundaries. Boundaries are something that can be easily misconfigured (or not configured at all). It's possible the former employee was only "testing" ?? and only added in boundaries for a test / pilot location? But this is just a wild guess....