Simple checks should be done without Zabbix agent, but it tries to convert this simple "net.tcp.service" check in an agent check.

Example Item:
Type: Simple Check
Key: ssh[{$SSH_PORT}]

The Webinterface does only accept it with [ ] brackets. The comma separated version like in documentation is not correct anymore. (But old items with comma does work). After few minutes Zabbix set Status to "Not supported" with following error message:
Simple check net.tcp.service[ssh[50022],85.25.29.5]] is not supported

The macro {$SSH_PORT} is global defined with value "22" and for this host with value "50022".

If we change the key for this item to ssh, {$SSH_PORT} directly in the database it will start working.