We are getting java.lang.IllegalArgumentException: Private key file could not be parsed. Exception

Hi Team, 

I have updated all the necessary information pdfservices-api-credentials.json and also mentioned the path for  private.key file but after reading the private.key information i am getting below exception.I have downloaded the private.key (config.zip) information.

org.bouncycastle.util.encoders.DecoderException: unable to decode base64 string: invalid characters encountered in base64 data

Can anyone help me what could be the exact fix for this .If anyone need the sample file format please let me know so that i will share it.