UnsupportedOperation: truncate

Question

I'm trying to write my Dataframe in a new sheet in my excel file, but this returns to me UnsupportedOperation: truncate

with pd.ExcelWriter('excel.xlsx', mode = "a", engine="openpyxl", if_sheet_exists = 'replace') as writer:
  df.to_excel(writer)
---------------------------------------------------------------------------
UnsupportedOperation                      Traceback (most recent call last)
<ipython-input-7-60abc31742f2> in <module>
      1 with pd.ExcelWriter(pricing, mode = "a", engine="openpyxl", if_sheet_exists = 'replace') as writer:
----> 2     Dados.to_excel(writer, sheet_name = 'Dados', index = False)

c:\users\família\desktop\ian\lib\site-packages\pandas\io\excel\_base.py in __exit__(self, exc_type, exc_value, traceback)
   1199 
   1200     def __exit__(self, exc_type, exc_value, traceback):
-> 1201         self.close()
   1202 
   1203     def close(self) -> None:

c:\users\família\desktop\ian\lib\site-packages\pandas\io\excel\_base.py in close(self)
   1203     def close(self) -> None:
   1204         """synonym for save, to make it more file-like"""
-> 1205         self.save()
   1206         self.handles.close()
   1207 

c:\users\família\desktop\ian\lib\site-packages\pandas\io\excel\_openpyxl.py in save(self)
     82         if "r+" in self.mode and not isinstance(self.handles.handle, mmap.mmap):
     83             # truncate file to the written content
---> 84             self.handles.handle.truncate()
     85 
     86     @classmethod

UnsupportedOperation: truncate

If I try to write a new excel file it works, but it's not what I want