Css styling not working on one table?

I am making a change to an existing page. I need to redo the existing table.

The program is clunky so I copied the css file into an editor and then built my table there. Everything looks great - css, everything.

When I copy that table code back into my program it:

loses all CSS stylesSHAREit

-overlaps the existing table (even tho it’s in a div)

I’m a back end dev and have Less experience with front end stuff. What could be messing this up?SHAREit