What causes the error message:
VAN0850E TCP/IP Request: INITAPI failed, ERRNO= 156
GENTCPSV FAILED DURING INITIALIZATION
This ERRNO indicates a z/OS UNIX process initialization failure.
This is usually an indication that a proper OMVS RACF segment is not
defined for the user ID associated with the application.
The RACF OMVS segment might not be defined or might contain errors such
as an improper HOME() directory specification.
Attempt to initialize again. After ensuring that an OMVS Segment is defined,
if the errno is still returned, call your MVS system programmer to have IBM
service contacted.
This info is for the 156 error number that can be found here...
https://www.ibm.com/support/knowledgecenter/SSLTBW_2.3.0/com.ibm.zos.v2r3.cs3cod0/syserret.htm