There is an identical issue here I can't respond to:
I tried following the advice from the person who responded but I can't get past the steps about force stopping Google play services and Google play store. I do that, and I still can't even get Google play store to start. Yes I've updated the OS and yes I've done a hard restart.
Thanks for reaching out and thanks for being a step ahead of us.
A few questions: what specific apps are you trying to download? Are you getting any messages when downloading the apps? What country are you in? When you say you do a hard restart, does this mean that you performed a factory reset on your Chromecast?
Please take note that not all Google Play Apps are compatible with your Chromecast with Google TV. If the app is not compatible, it won't even show up in the Google Play Store app when you search. Try to reboot the Chromecast and plug it in on a different HDMI port on your TV.