The ads.txt file was successfully updated, however, the message has not disappeared from the dashboard.

Please make sure you added all the ads.txt lines and that they are correct. Also, double-check if they were added to the correct domain. Also, please keep in mind that it may take up to 1 hour for the system to update the information about your website.
If all was done accordingly, please try clearing cache and cookies and logging in again. The message should disappear.
In case you tried everything and the message still shows, please contact your manager to solve the issue.