That should work, but make sure you restart both of the Wowza Streaming Engine services, and ensure that entries are being written to the new location.
If the new location is a network drive, make sure that the Wowza services have access to the share (you may have to add a login user to the services if there are insufficient privileges).
I did check on this and, at least currently, the logs are only read from [install-dir]/logs and therefore the log4j.properties entries are ignored.
So what’s probably happening in your case is based on log4j.properties the logs get written to one place, but the log viewer expects the logs in the default location.
If you’ve already moved the logs then obviously they will not be found.