I have never been able to update Factorio since upgrading it to 0.17.2. The updater always says that there is a new version but it can't be downloaded automatically.
It only says that after manually checking for updates. The automatic update run on startup is completely silenced.
I started using the 0.17 branch with 0.17.2. Updating to 0.17.6 was not possible automatically so I downloaded it manually.
Updating from 0.17.6 to 0.17.9 also seems to be broken and I have to download it manually again.
Running portable on W7 x64
[0.17.X] Unable to update within the 0.17 branch
Re: [0.17.X] Unable to update within the 0.17 branch
This is known and mentioned in the changelog.