DCU not updating to 4.9.0

Never had a problem with past versions updating themselves, but my 365 defender dashboard started flagging 4.8.0 as having a security problem and I wondered why DCU wasn't taking care if it.  Manual search/update isn't finding it, the only way I've found to update to 4.9.0 is to manually install it.

Any idea what changed to make it stop updating itself?