Of course, since you removed your dll.xml and exe.xml files so fix your pmdg problem, those do not contain the lines needed for our sceneries to work anymore.
So, you simply need to reinstall our scenery so, our installers will put the needed lines back.
Note that, this is not specific to our sceneries: if you have other addons that requires modules to be installed either in dll.xml or exe.xml, you need to reinstall all of them, for the same reason.