Yeah this happens quite often, due to whatever reasons
![Frown](//cdn-eso.mmoui.com/images/style_esoui/smilies/frown.gif)
If a reloadui does not work, and a logout and login again does neither work, you often are forced to quit the whole quest row and redo some parts...
I alway search the web and official ESO forums for solutions first, and UESP as well as it often got additional quest infos:
https://en.uesp.net/wiki/Online:Quests
And if you cannot find any help there, ask ingame in the zone chat. At the bitter end you sometimes need to abandon a quest line and redo it from whatever point the game then says you will start again
![Mad](//cdn-eso.mmoui.com/images/style_esoui/smilies/mad.gif)
But it'd always first search the web up and down, ask in guilds. Maybe someone experienced the same or similar.