Error Importing SSL certificate : Not an X.509 Certificate

I am trying to Update the SSL certificate in accordance with this post .

I am noob in certificates, so i followed this guide. But, when i enter

keytool -keystore mycacerts -storepass changeit -importcert -file "C:\Users\Noks\Desktop\cacerts.pem" -v

I get the error:

keytool error: java.lang.Exception: Input not an X.509 certificate
java.lang.Exception: Input not an X.509 certificate
        at sun.security.tools.KeyTool.addTrustedCert(KeyTool.java:1913)
        at sun.security.tools.KeyTool.doCommands(KeyTool.java:818)
        at sun.security.tools.KeyTool.run(KeyTool.java:172)
        at sun.security.tools.KeyTool.main(KeyTool.java:166)

How do i fix this?

Does your cacerts.pem file hold a single certificate? Since it is a PEM, have a look at it (with a text editor), it should start with

-----BEGIN CERTIFICATE-----

and end with

-----END CERTIFICATE-----

Finally, to check it is not corrupted, get hold of openssl and print its details using

openssl x509 -in cacerts.pem -text

Many CAs will provide a cert in PKCS7 format.

According to Oracle documentation, the keytool commmand can handle PKCS#7 but sometimes it fails

The keytool command can import X.509 v1, v2, and v3 certificates, and PKCS#7 formatted certificate chains consisting of certificates of that type. The data to be imported must be provided either in binary encoding format or in printable encoding format (also known as Base64 encoding) as defined by the Internet RFC 1421 standard. In the latter case, the encoding must be bounded at the beginning by a string that starts with -----BEGIN, and bounded at the end by a string that starts with -----END.

If the PKCS7 file can't be imported try to transform it from PKCS7 to X.509:

openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer