In the free listings section of Merchant center, we were seeing daily traffic of about 33K-36K impressions in free listings prior to the Google review algorithm update. The reviews we had did not have schema, but we were getting that set up, mostly from 3rd party reviewers on our products (cell phones). Since April 11th our traffic has dropped to about 2,500 impressions. We finally have gotten the schema set up in the pages, but we are not seeing any uplift.
I have submitted this to the Google developers forum and was told that the changes may occur after the next update. I am trying to see if thereis any other reason. FYI, we do take the site down for maintenance for about 8-10 hours 1x/week.
Any help in this is greatly appreciated.