Steps to reproduce:

1. install Zabbix Server from Docker zabbix/zabbix-server-mysql:ubuntu-4.4-latest
2. configure Host in Zabbix with trapper and hostname item, encryption psk
3. install zabbix agent and configure psk
4. use zabbix_sender to send values to zabbix server (trapper item)

Result:

PSK Encryption active:
zabbix server gets data for agent.hostname (Zabbix passive)
zabbix_sender can not send Data (see atachement)

Encryption deactivated:
zabbix server gets data for agent.hostname (Zabbix passive)
zabbix_sender can send data to trapper item

Setup:

Zabbix Server 4.4.4: installed as Docker container on rancheros

Zabbix Agent 4.4.4 and 4.2.8: Installed on Ubuntu 18.04

Expected:
Send Data with zabbix_sender and use Active Checks over PSK