the PDP involves the GGSN, so a low success rate might mean that the PDP is unable to understand the APN defined in the MS, or unable to provide an IP adress, or there is some mistake in the QoS profile.
APN is a character string written in the MS, either by default, by push-configuration or by the subscriber. This name (for instance “net”) would be then interpreted by the GGSN, in order to understand what is needed by the MS.
HTTP ? FTP ? WAP ?
Depending on the required service(s), a certain IP adress can be allocated to the MS.
But ff the APN “string” is not in the GGSN, then I guess the GGSN is not able to allocate a PDP context.
Are you sure it’s not “APN” rather than “ANP” ? If missing APN, it means you didn’t input the APN parameters in your phone for the data service you are asking for (usually, one APN for MMS, one APN for web)
Check your phone settings & operator guidelines to configure it.