Difficulty to import CA certificate on FortiGate 7.6.7

Hello, I am unable to import the CA certificate onto FortiGate 7.6.7. I generated a certificate using AD CS and am trying to import it into the FortiGate, but I receive an error stating that the certificate format is incorrect. Note that this CA was used to sign the FortiClient EMS SSL certificate. This is for a ZTNA lab setup where I want to integrate FortiClient EMS 7.4.8 with FortiGate. I am using evaluation licenses.