The message 'Exceeded permitted concurrent web requests. Please retry later' shows up when a user attempts to run more than 3 reports simultaneously at any given time, and is independent of the browsers being used. This restriction is set in place by Replicon to ensure optimal performance without restricting regular access.
Please wait for any one of the existing 3 "Run Report" actions to complete. Once the number of concurrent requests drops to 2 or below, you can run the report you were attempting to when the error occurred.