the new x64 installer updates only ver. x86 to 1.28 bit_comet_x64.exe remains 1.27
Your shortcut (link) is pointing to the wrong location. Go the the icon where you launch bitcomet, “right click” and select “properties”
Change the target to “c:\program files\bitcomet\bitcomet.exe”
Yours probably has something like “program files (x86)\bitcomet_x64.exe”, which is how version 1.27 did it. When 1.28 installs, it makes new shortcuts, but it cannot change ones that windows generated without it’s knowledge, like on your quick launch menu.