I would not blame the reverse proxy for that, the only thing I know that prevents logging is if file system permissions got messed up and it cannot write to the log file, the same problem could also be why file upload is not working.
the user that is the identity on the application pool must have full control on /Data folder and all files and folders below it. sometimes the permissions on a folder might be ok but on existing files such as the log file /Data/currentlog.config the permission is bad, so you may need to fix not just folder permissions but permissions on some existing files.