FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
Article Id 192481
This article explains how to avoid  the SSL VPN connection failing at 98% due to "Modem Removed- Unavailable device ()".

Under fortissl properties, on the "General" tab, in the "Connect using:" box, it shows "Modem Removed- Unavailable device ()"


1) Open Network Connections.  The "fortissl" connection will be showing the device message "Unavailable - device missing".

2) Open the properties for this connection.

3) On the "General" tab:
a. Uncheck the "Modem Removed – Unavailable device ()" device.

b. Check the "ISDN channel - PPPoP WAN Adapter" device.

c. Click the up arrow on the right to move the "ISDN channel - PPPoP WAN Adapter" to the top of the list.

d. Set the phone number for the "ISDN channel - PPPoP WAN Adapter" to 1.

4) Click "OK" to close the "fortissl" properties.

5) The "fortissl" connection should now appear greyed out with the device message "PPPoP WAN Adapter" and a status of "Disconnected".

It should now be possible to successfully establish an SSL VPN connection.