DIAGNOSIS This is almost always a Wi-Fi connectivity hiccup. The camera has power but can't talk to your router consistently, usually because of signal strength, network congestion, or a router setting.
FIX First, restart the whole chain. 1) Unplug the camera's power cable from the wall. 2) Unplug your Wi-Fi router and modem for 30 seconds, then plug them back in and let them fully boot. 3) Once your internet is back, plug the camera in. Give it a few minutes to reconnect. This clears up most temporary network glitches.
IF THAT DIDN'T WORK The camera might be too far from your router. Check the signal strength in the Google Home app under the camera's settings. If it's low, try moving the camera closer temporarily to see if it stays online. If it does, you might need a Wi-Fi extender or to reposition your router.
HEADS UP Some routers have a "band steering" feature that can confuse smart devices. Try temporarily splitting your 2.4GHz and 5GHz networks into separate SSIDs and connect the camera only to the 2.4GHz one during setup—it's more reliable for these devices over distance.