Lyrics are only displayed if the lyrics have been added by the lyrics in your region, and if Spotify has the license to display the lyrics in your region. Different regions have different lyrics providers. For me the lyrics provider in my region is Musixmatch, but there might be a different lyrics provider in your region.
If the lyrics provider is Musixmatch, depending on who addeds the lyrics, it can take a while before the lyrics apperar in the Spotify client. The lyrics usually appear after some days if the one who added the lyrics have "curator status" on musixmatch, but if they do not have "curator status" on musixmatch their submissions needs to be upvoted by other users before they are approved, which can take a long while depending on how much time it takes before the lyrics are reviewed and approved.