Strange, yes; maybe if Youtube’s automatic translation is having issues and you’re not a Pro LR user, that is making LR display the " - " ? (Not sure I am a relatively new user—since July-ish)
Are your settings for LR on “Human Translation,” or is your “Machine Translation” toggled on?
LR can only pull what the Source material has for subs, but for pro users, the “machine translations” can be toggled on to show translations generated from the original language in the video.
But, if the subtitles uploaded by the Youtuber/original uploader of the video messed up the subtitles or properly labeling the language of the video, it will result in the translations getting messed up by both Youtube automatic translation and LR’s machine translation (plus the “human translation” option, if the translation is really just the auto-generated version of subtitles from YouTube).
Edit: I also found this reply on a similar Forum post in #ask-the-community that goes into some further detail: youtube translation language not showing up - #23 by Alx02