It is a little hard to answer this question without being able to look at the service with the issue. If you are sure the file exists, I would be checking there is no issues with casing of the file name. Your service runs on Linux where the filesystem is case sensitive. The case of the filename will have to match 100% other Linux will not be able to find the file.
It could also really be a permission error, so I would make sure the file has 644 permissions.