Make sure misconfiguration of Azure MFA does not result in a failed install
If Azure MFA is turned on as one of your authentication methods and not actually configured, it will result in a failed install:
To remedy this go to the ADFS management console and edit the Multi-factor Authentication methods:
In the policy window which pops up, ensure that Azure is unticked:
You can then proceed to run the ADFS plugin installer. Note that there is no need to restart the server for these changes to take effect.
Using a proxy for outgoing connections
Note that, if using a proxy to configure extranet access, it is important that your proxy settings do not interfere with operation of the ADFS plugin.
For example, make sure that your whitelist does not block any connections.