I got the same problem, the virus signature database is stuck at 15315. "Update Now" does nothing, just tells me that its already up-to-date but the home screen tells me that its out of date. The client was also stuck at 10.0.390 and didnt see 10.1.210, but this was fixed by downloading the client and running the setup.
Had to rename the file to .etl.log as the extension .etl apparently isnt allowed.
updater_20170608_180530.etl.log