So when you created the empty cache for the service with "manual", did it create the folder and structure in the arcgisserver folder?
Have you told it how you want the scales, etc. setup all ready...and do you know/expect it to be the same as the folder that contains the cache already?
If so, you should be able to compare the config.xml files from the new blank cache folder structure, and the one you will use the replace it. They need to be exactly the same to do a replace by rename or by moving the L00...Lxx folders over.
We are still on 10.2.2, but the structure should be about the same (our caches and other files are on our D drive)
arcgisserver- ImageServicesrFolder (our image services have another folder layer)
- ImagerServerName_ImageServer ( the conf.cdi and conf.xml files are here)
- _alllayers
- L00 .... folders with the bundle and bundlex files
- status.gdb
- MapServiceName1
- Layers ( the conf.cdi and conf.xml files are here)
- _alllayers
- L00 .... folders with the bundle and bundlex files
- status.gdb
I hope that makes sense. I wanted to point out that Image Services themselves seem to put all those services in the Folder structure that we have on our server...and the actual service folders have _ImageServer in the name. On the other hand, the Map Services seem to have the servicename folder right below the arcgisserver folder (and ignores the folder they are separate into). This may be a 10.2.2 thing....just getting started on 10.5.x testing so things may be different in 10.3+ (??)
Just a thought....the cache folders....was the cache created on the same server, or on another and moved over? It may be a permission thing. Make sure that the same permissions are assigned to all the folders/files in the renamed cache folder as are on and folders/files on a new service.
Also, make sure the cache is a compatible version. If it was created in an older or newer version you may need to try to Import the cache (I seem to recall is a tool for this in 10.3) or possible expand the files from the bundleX and then convert them back into the 10.3. compatible format. There was a bundlex format change between a couple of the versions, and it may have been 10.3. now that I think about it. I had test 10.3, we just never implemented it (by choice do to hardware upgrades needed, etc.)
If all else fails, but you know the cache is correct, I would remove the service giving the error, restart ArcGIS Server (reboot), make sure you have the folders setup correctly, and try is again. Sometimes caches can be finicky, but I do this process all the time, so I know moving them around works.
Hope that helps and isn't too rambling.