It is well known that IPsec VPN dial-up is not shown on the FortiGate interface widget because of design and the VPN is not up all the time.

There is a different way to monitor an IPsec VPN dial up as described here.

Using FortiCloud it is possible to monitor and see useful information about the IPSec dial up VPN.
Expectations, Requirements
1. IPsec dial up VPN already configured and up & running

2. A FortiCloud basic account

At the FortiGate:

1. Make sure that firewall policies for the IPsec VPN has "Log all sessions" enabled

At FortiCloud:

1. IPsec VPN dial up is already up & running

2. Login to FortiCloud

3.  Go to FortiView --> VPN Tunnel

4. You can also see the info at FortiView --> Source and verify the IP address range delivered by the VPN.