If your firm has Onvio VAT only and you're using Onvio Link to uplift clients from Digita Practice Management, there's no need to act on this message. Just close the message dialog and continue with the uplift.
If you're attempting to use Onvio Link to open documents locally, contact the person appointed as the Onvio administrator for your firm to ask if you lack a specific permission or if the firm lacks the necessary licence.