Latex overline underline doesnot effective

Steps to reproduce

When I use latex formula, underline and overline doesnot effective when the quoted words longer than 1 word.

Expected result

when typing

\overline{\lim}

it should be an overline over lim. Similar to underline.
However, if the overline quated only one word, the overline is OK.

Actual result

image

Environment

  • Operating system:
    win10

Additional information