The tagging method for Google Assistant was deprecated 1.5 years ago, but they were left in place to give time for people to move over to the metadata approach, ideally as they transitioned to OH3.
The problem is that we don’t have a way of communicating this to all users, other than the community. So while it was big news when the change happened, there was no way to inform users who don’t check in on a regular basis. Unfortunately, we have to wait for them to come here and ask when it stops working. And as you’ve discovered, it keeps working until you refresh your devices in GA.
Assuming that you’re using .items files, you’ll replace all of the GA tags (e.g. [switch] ) with metadata, which is contained in the {} brackets with the item’s channel.
{channel="", ga=""}
There are also many more options for item types (made possible by the metadata approach).