The issue is related to store connection in Webgility Online

1). Go to Settings> Connection

2). Click on Edit Connection and select Update Credentials

3). Click on Continue to update the credentials and test the connection

If the error still comes please check the store permissions and get this done from the store backend to allow full permission for the Webgility application and try again to test the connection in Webgility

Note: If the error still persists please contact Webgility support.