I try to create .pem file from .p12 file with this command

openssl pkcs12 -in voip_services.p12 -out voip_services.pem -nodes -clcerts

Previously it works fine but my pem file will expire in few days so I try to create new .pem file but this gives me ssl error

Error:OpenSSL SSL_read: error:14094418:SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca, errno 0