.pem file gives ssl error

I previously create .pem file for voip push notification and it works without any issue. But when I try to create another .pem file same way as before it created the .pem file but throws ssl error

I create the .pem file with this command

openssl pkcs12 -in voip_services.p12 -out voip_services.pem -nodes -clcerts
Error:OpenSSL SSL_read: error:14094418:SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca, errno 0