Self signed certificates are not trusted because the underlying website may pose a security risk to you. Most applications, including Lunar Client, will reject these types of certificates to protect you from potential danger. An application you installed may have modified your computer's hosts file, redirecting some Mojang domains to a different website. To fix this, you will need to clear out specific entries in your hosts file., which stores the redirects. 


Depending on your operating system the solution may slightly differ:


Instructions (Windows)


Step 1: Run Notepad as Administrator

  1. Press the Windows key to open Search.
  2. Type in "Notepad", then press the "Run as administrator" button.



Step 2: Open hosts file

  1. In Notepad, press the "File" button at the top left, then press "Open" in the dropdown box.
  2. In the window that opens, copy and paste "C:\Windows\System32\drivers\etc\hosts" into the text box at the bottom.
  3. Press the "Open" button at the bottom right.



Step 3: Delete hosts file entries

  1. At the bottom, look for any lines that contain "mojang.com". These lines will not begin with a hashtag.
  2. If any of these lines appear, delete them completely.



Step 4: Save the file

  1. Press the "File" button, then press "Save". Do not press the "Save as" button.



Instructions (MacOS)


Step 1: Launch the MacOS Terminal application

  1. Go to "Finder" and click "Go".
  2. Within the dropdown click "Utilities
  3. Locate "Terminal" and open it.


Step 2: Open hosts file

  1. Enter the command sudo nano /etc/hosts into the Terminal.
  2. When prompted enter your administrative password to allow access to the file


Step 3: Delete hosts file entries

  1. At the bottom, look for any lines that contain "mojang.com". These lines will not begin with a hashtag.
  2. If any of these lines appear, delete them completely.



Step 4: Save the file

  1. Press Control+O to overwrite the existing file, then press Enter to confirm the overwriting. This saves the changes to the file. 
  2. Press Control+X to exit the nano editor.


Step 5: Refresh DNS records

  1. Enter the command sudo killall -HUP mDNSResponder into the Terminal.