KCP module requires the script pp_cli to run on the server for sending a payment request.

this file is 32bit, so in some cases, you must make sure 32bit runtime library files are installed on your 64bi machine
apt-get install lib32gcc1 libc6-i386 lib32z1 lib32stdc++6
apt-get install g++-multilib

make sure the pp_cli file is executable. test by running ./pp_cli -h in the terminal and check if the output is given.