We are so sorry for this inconvenience.
Shopify upgraded API, and Ryviu might get trouble when accessing your store so please follow exactly the steps below to update Ryviu app to fix this issue and reconnect your store with Ryviu:
STEP 1: Log in to your Shopify admin > open Apps, then click on Ryviu - Product Reviews to log in to your Ryviu account:
STEP 2: Update Ryviu app
Open this link below, click UPDATE APP button to fix this issue.
You are done.
Thank in advance,