As you can see, they are completely gone. However, if I go to preferences > presets > show lightroom develop prests .... they are all there. I try to re-import them and it says they are already imported.
Your screenshot shows "The file could not be found", which means the photo on disk is "missing", no longer at the location recorded in the LR catalog (e.g. you moved or deleted the file with Finder / File Explorer). In this case, the Presets panel won't show you presets or let you manage them. Edit a photo that isn't missing (marked with "!" in Library grid view), and you should see your presets.