title: The dataframe read from xlsx file edited by openpyxl is empty
body: <p>I've used openpyxl to edit the formulas in my table and save it as a new xlsx file. After doing these, I directly applied pandas to read this new xlsx file, but what I got is an empty dataframe.</p>
  <p>Having found this, I open the new xlsx file and click the 'save' button. Then, pandas can read this file as expected.</p>
  <p>What I'm wondering now is why this issue happened and how can I avoid the 'save' step.</p>