There are numerous cases of businesses losing all of their reviews that they have acquired over the years in their Google Business Profile listings. The issue seems to be related to Google automatically applying suggested edits from the web to those business profile listings, which in turn can create a new CID for that business listing, and with that, the reviews get disassociated from that business listing. The result, when you look at the business listing in Google Search or Google Maps, the reviews no longer exist.
The report. Mike Blumenthal covered the issues in greater detail where he documents