@Annggela24 It has happened to me twice.I kept using the glucometer to measure and the diabox in the mobile.The LibreLink app detected error failure and told me to replace. The pirmera once the glucometer also gave me a failure two days later;The second time I ended the 14 days of the sensor with the glucometer and Diabox without problems.
In my opinion you have to have both assets in case one fails.