Hi, I have 115.12.2 (64bit) Thunderbird installed in to my Windows 11 desktop PC. I have been using Source Sans 3 font as the default message font for at least five yeasr. This font is selected as the default font for composition as well as html style. Unfortunately Source Sans 3 is shown as "not installed" in the font list for about six months. Whenever I reinstall it to Windows 11 everything starts to work perfectly until I restart my PC then Thunderbird starts to show Source Sans 3 as "not installed". I am able to use this font with the Libreoffice. I tried the same procedure with Source Code with identical results. Can someone help me please? Serkan Alkan