Open Settings and tap Profile Downloaded near the top.
Tap Install in the top-right corner and enter your passcode.
Mandatory Step for iOS:
Go to Settings > General > About > Certificate Trust Settings.
Under "Enable full trust for root certificates", toggle ON trust for Fortinet_CA_SSL.
Tap Download Certificate (.crt) above.
If prompted by Android, select CA Certificate or Wi-Fi Certificate.
If not prompted, open Settings → Search for CA Certificate.
Select Fortinet_CA_SSL.crt from your Downloads folder.
Click Download Certificate above and double-click the file to open.
In Keychain Access, find Fortinet_CA_SSL under login or System.
Double-click the certificate and expand Trust.
Set When using this certificate to Always Trust.
Close Keychain Access and enter your Mac password to confirm.