I have tried this too. However when I go to Google store it says the app is already installed but can't find it anywhere. I even tried the link supplied by someone on here but once again is saying it is already installed.
I'm no expert but I think it's trying to use the app that's the problem, I just open SAFSEE in the Chrome browser and cast from there, no app involved, full screen onto my old (now small it seems) 36in Smart TV
Unfortunately my chrome browser is not recognised on the TV only when I open an app??? Frustrating to say the least. Is there a button somewhere on the chrome Browser to cast as I am open chrome cast via Google home and wonder if the problem lies there.
I just browsed the Internet on the TV and did a search for my vpn and logged in. Then I opened the SAFSEE app. Still not sure why it's not working properly. I even tried it on a different smart TV