I know nothing about Homeseer but it sounds like you do not have the EZSnsRF linked to the powerline controller being used by Homeseer. You can trigger from an Insteon message being sent from the SwitchLinc I assume because that device is linked to the Homeseer powerline controller. The EZSnsRF will send messages only to the devices that have been linked to it. The SwitchLinc is linked to the EZSnsRF as it is responding to the Insteon message generated by the receipt of the Dakota Alert RF signal. If Homeseer will not trigger from the same condition it is likely that the Homeseer powerline controller is not linked to EZSnsRF so it does not “see” the Insteon messages being sent to the SwitchLinc. Again just from an Insteon perspective, without that link the only way Homeseer would know if the SwitchLinc is On or Off from another device would be to Query the SwitchLinc on some time basis.
The Simplehomenet Utility Suite is a free download available on the Downloads section of the SHN web site. The Utility requires a PLC or EZSrve device to interface to the powerline. The Utility does not support a standalone PLM as a powerline interface.