How do I import files to the library to show the date they were imported?
Is your question about Lightroom (Lr icon) or Lightroom Classic (LrC icon)?
Where would you want this information about date imported to show?
Repeating my earlier question: "Is your question about Lightroom (Lr icon) or Lightroom Classic (LrC icon)?"
Also, when I ask "Where would you want this information about date imported to show?" it does not help to state that it used to show. I still don't know where you want to see this (or where you previously would see this).
Since you haven't answered any of the questions, I'm going to guess.
Either that you used to see Previous Import in the Catalog panel, which is a temporary collection which changes every time you do a new import.
If you want to see this collection every time you import, go to Preferences > General, and check Select the "Current/Previous import" collection during import.
Or, you have been using the Filter bar (press Ctrl+L and/or backslash if you don't see it) to show photos taken on a certain date.