Greetings @Sequoya ,
Less than a month ago all servers from North America and Asia were changed and when this happens the favorite servers may disappear from your list, which means that you need to manually access the server again so it can be set as favorite.
You can find more information on the following post: IP changes for Official Servers
You should be able to see on the event log what happened. If you find any thing unusual happening in the event log, please feel free to contact our support team though help desk with a screenshot of the event log: https://funcom.zendesk.com/hc/en-us/requests/new
We wish you a great day!