Thread:Su712/@comment-2600:1700:EB91:9C20:420:CF9C:7144:CCD4-20180129015828/@comment-31479589-20180129042304

That's a well-known glitch, where the boss icon disappear, therefore preventing you from fight them again. It's suppossed to be fixable by completing Interlude, so I'm confused as well :/

Probably try to turn on your internet connection, some of the files may be damaged and the game will prompt you to download again.