Whoisonmywifi app shows unknown computer on Network but the router doesnt see it

[k1701]

Hello everyone,
First time poster, I have an issue with my network. I use whoisonmywifi free app to help in my network security.The app picked up an unknown computer on my network,
I took note of the device's MAC address and accessed my router's settings page(192.168.1.1)
and entered it into the MAC filtering page to block it.
The MAC address is listed as being blocked on the filtering page, routine scans by the whoisonmywifi app shows the unknown pc is still connected.

my questions are:
1. Is there anything I can do block this pc?

2. Could be possible that it is a "ghost mac address" and it is not really online?

3. Should I just reset my network with a new name and password, do not broadcast SSID?

My router: Linksys WRT AC1900(most recent firmware update,) WPS2 Personal, Windows 8.1


Any help will be greatly appreciated

 

[ddw]

Could it be your ip provider? Comcast has hot spots on all new routers. They will turn it off if you complain.

 

[ddw]

Comcast has hot stops on all new routers. They will turn it off if you complain.

 

[k1701]

Comcast has hot stops on all new routers. They will turn it off if you complain.

Hello ddw,
Thank you for your response, I rebooted my router, and hid my SSID, I no longer see the unknown ip address,who is my WiFi app lists the ip as offline, also my Internet provider was making upgrades and changes, so it appears that was the problem.

Thanks for your advice!