What should a user do to successfully connect to a failing SSL VPN?

To successfully connect to a failing SSL VPN, changing the SSL VPN port on the client is a valid step. There are multiple reasons why SSL VPN connections may fail, and one of the common issues is that the default port being used for the SSL VPN might be blocked or in use by another application. By changing the SSL VPN port on the client, you might bypass configuration conflicts or restrictions imposed by a network firewall or local security settings, allowing for a successful connection.

While the other choices also address potential connectivity issues, they are not the primary or most immediate solutions for resolving a direct SSL VPN connection failure. Updating the firmware on FortiGate appliances is generally more time-consuming and may not directly address an immediate connection issue. Verifying group membership in the VPN configuration is important but presumes that all settings are correctly configured already; if the VPN was operational prior, membership changes would not be the first action to take. Disabling active firewall rules could be a solution, but the user may not have control over the firewall settings, making this less applicable to a user-level action compared to simply adjusting the client.