The issue appeared to be a formatting issue in the import file. Some generic recommendations if you get import errors:
- line-ends in the import file should be either DOS (CR+LF) or UNIX (LF). If you create the file on a UNIX system or MAC, or in Notepad on Windows, that should be good. With Notepad++ on Windows, you can select the line-ends.
- When you receive certificates, sometimes there is a header that describes the certificate. Make sure that your import file has only the certificates itself as I showed above:
-----BEGIN RSA PRIVATE KEY-----
MII.......
<Private key here; I assume it can be a the end as well, I prefer to stick it here. It can be encrypted or unencrypted, if encrypted the passphrase should match>
............BJD1DnCs2W
-----END RSA PRIVATE KEY-----
-----BEGIN CERTIFICATE-----
MIIEfTCCA2WgAwIBAgIDG+cVMA0GCSqGSIb3DQEBCwUAMGMxCzAJBgNVBAYTAlVT
<Server certificate here, issued by intermediate 1>
qm5vjLyb4lddJIGvl5echK1srDdMZvNhkREg5L4wn3qkKQmw4TRfZHcYQFHfjDCm
rw==
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
MIIE0DCCA7igAwIBAgIBBzANBgkqhkiG9w0BAQsFADCBgzELMAkGA1UEBhMCVVMx
EDAOBgNVBAgTB0FyaXpvbmExEzARBgNVBAcTClNjb3R0c2RhbGUxGjAYBgNVBAoT
EUdvRGFkZHkuY29tLCBJbmMuMTEwLwYDVQQDEyhHbyBEYWRkeSBSb290IENlcnRp
<Intermediate 1 certificate here, issued by the root CA>
GIo/ikGQI31bS/6kA1ibRrLDYGCD+H1QQc7CoZDDu+8CL9IVVO5EFdkKrqeKM+2x
LXY2JtwE65/3YR8V3Idv7kaWKK2hJn0KCacuBKONvPi8BDAB
-----END CERTIFICATE-----
Remove everything that is in front of the BEGIN or after the END lines of the initial file so you only keep like the example above with END and BEGIN lines head-to-head without anything in between.