I just found out by manually exchanging the addon files and Nemulos Objekte? sorry for the miss spell. But the program is looking for the .sco files with the UMLAUT the umlaut is not on the files in the current version of simple streets and the Objekte folder, even the ADDON_gCW, there are no umlauts, that is the problem,
So any one kind enough to translate this for the german side, please do as it's necessary, but that is the case, no umlauts, the files are exactly the same name but OMSI can't differentiate between no umlaut and plain written text.