Polk Magnify Mini is showing in Google Home as " offline" even though connected to wifi

My Polk Magnify Mini is showing in Google Home as " offline" even though it is connected to the same wifi as my mobile. I am able to cast music from my phone to Magnify Mini. But since it is showing as offline I am not able to make this as a default speaker of my Google Nest Mini. I don't think this a problem of wifi since I am able to make my Sonos Era 300 as a default speaker of my Google Nest Mini. Please suggest what I can do to make Polk Magnify Mini as my default speaker. I have already done a factory reset of Polk, Wifi reset , AP Isolation off for wifi.