To work with HTTPS web sites, VSO Downloader must act as a "Certification Authority" (CA) for your web browser.
The installation of VSO Downloader usually deal with all the burden of installing those certificates in the browser's certificate store.
However, for some reason totally independent of VSO, Firefox sometime erase the VSO Downloader CA certificate from its certificate store. This is may occur when Firefox auto-update itself, or is updated manually.
If this is happening, when using VSO Downloader and with HTTPS support checked, Firefox will display the website as "unsecure", and may even refuse to connect to them.
Downloader can automatically reinstall this certificate in Firefox.
- Automatic reinstallation of Firefox certificates
To fix the situation, the VSO Downloader CA certificate must be reinstalled in the Firefox certificate store manually.
This is done with the following procedure (click on the image below to expand / save it at full size ):
- How to install VSO Downloader CA certificate in recent Firefox after an update.
2 - Select Options
3 - Select Privacy & Security - on some firefox version, it might be in Advanced, section Certificates
4 - Click on View Certificates ... button
5 - Click on Import ... button
6 - Select the subfolder 'certificate' in VSO Downloader installation folder (typically "C:\Program Files (x86)\VSO\VSO Downloader\5\certificate")
7 - Select certificate ca_sha2, and click Open
8 - Make sure to have Trust this CA to identify websites. checked, and click OK
9 - Click Ok, close all Firefox Options windows / tab
Once this is done, https support in Firefox for VSO Downloader should be available again.