While Checking the expiry date of newly installed ssl it showing custom errr?

While Checking the expiry date of newly installed ssl it showing custom errr?

Am fully new to this site before setting this question as duplicate or
hold read this.
I am just installing sslcertificate which is in .pem for enabling
APplePush Notification but the newly installed .pem file not seemin to be
working proper. when i check for expiry date it showing the following
error
-bash-3.2$ openssl x509 -noout -in xxxxx.pem -enddate
unable to load certificate
11458:error:0906D06C:PEM routines:PEM_read_bio:no start
line:pem_lib.c:647:Expecting: TRUSTED CERTIFICATE
And notable one .pem file doesn't generated by us it is conveted and sent
by third party so say me what could be the problem. Thanks in advance