Hi There, Could anyone help me with this error

Welcome to the community, @BrOo! If you collect data with Enketo aka web form, the forms will be stored in the browser unless the device is connected to the internet. Once it is connected to the internet, the filled-up forms are automatically submitted to the server. You could also force-submit the filled-up forms to the server.

Details on the same are outlined in this support article Collecting Data through Web Forms.