I'm looking for the symbol to make a "check mark", but cannot seem to find it. I once used it in previous version of Office/Excel (2013), but cannot locate it in Office 365.
You could click on the Insert tab, Symbol, and select either Symbol or Wingdings2 font. I believe those both have a check mark. Or, hold down the Alt key and type 0252 on the number keypad and change the font to wingdings.