Environment IAP 18.104.22.168-4.0 and above
Instant supports the following certificate files:
Auth server or captive portal server certificate: PEM format with passphrase (PSK)
CA certificate: PEM or DER format
We notice this error when the private Key is not encrypted i.e without the passphrase
To view a list of server and CA certificate formats that are supported by the IAP, run the show supported-cert-formats command.