Hi Lidka,
One quick test you can do to check the cause is use the below entries in your alert.filter
<FILTER enable="true" name="myAlertFilter" source="NGSwitch">
<FILTER_ACTION_NAME name="Send Email"/>
</FILTER>
And instead of calling your custom class, use the email notification option. This can help us to know if the criteria is working , and corresponding action is been called.
Do send us the logs file if you still face any issue to nms-support [@] webnms [dot] com
Regards,
Ayush