Testing of alert fails

Hi guys,
when i try to test the alert it only says;
Testing the notification Test_Splunk failed. Alert script failed.

The splunk configuration is correct, it doesn’t matter which method i am using;
send to, scp…

thank you for your help!

GVM versions

gsa: (‘gsad --version’)
Greenbone Security Assistant 9.0.1~git-f4a4658fb-gsa-9.0
gvm: (‘gvmd --version’)
Greenbone Vulnerability Manager 9.0.1~git-0aae9d25-gvmd-9.0
openvas-scanner: (‘openvassd --version’)
OpenVAS 7.0.1
gvm-libs:
gvm-libs 11.0.1

Environment

Operating system:
Distributor ID: Ubuntu
Description: Ubuntu 20.04 LTS
Release: 20.04
Codename: focal

Kernel: (‘uname -a’)
5.4.0-33-generic

Installation method / source: