As of 3:07pm, 7/22/2020 CST, the issue should now be resolved. Everyone should be able to add their servers to the list.
We're currently investigating an issue with the verification process of adding a server to the list.
We will update this post when a fix has been released.
We apologize for the inconvenience and ask anyone who truly wants to get their server listed to contact us with your server ip, server port, the name for your server, and your Gemini username and we will get your server added for you in the meantime.
~Codewow
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