Use 3 backticks before and after code/config (or select and press </> icon) to make it more readable and preserve spacing, which is important in yaml.
Do both of your files have the correct content?
certFile should look like like:
-----BEGIN CERTIFICATE-----
MIIDmDCCAx+gAwIBAgISBfsGbJvk20lIcmKqBC8+OMX6MAoGCCqGSM49BAMDMDIx
...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
MIIEVzCCAj+gAwIBAgIRAIOPbGPOsTmMYgZigxXJ/d4wDQYJKoZIhvcNAQELBQAw
...
-----BEGIN CERTIFICATE-----
keyFile should look like:
-----BEGIN PRIVATE KEY-----
MHcCAQEEIEs+gNvQkO0EX/AyI6dI0Hplb4G8pfRMyDD47MntDgTDoAoGCCqGSM49
...
-----END PRIVATE KEY-----