IndexError: Index out of range about flask-excel HOT 2 OPEN

This can be somewhat of necroposting, but i had a similiar problem and found some nuanses, that can help someone troubleshooting their apps:
1)Remember about case sensitivity, names of your sheets must be EXACTLY the same as your models names

2)If in your model you use syntax like:

class Documents(db.Model):
    __tablename__ = 'My documents'

Then your sheet name must be 'My documents', not just 'Documents'

3)The number of sheets in your excel file should be the SAME as number of tables you use in 'tables' parameter of save, plus point 1&2 of my comment.
For example, i had an IndexError because after i added sheets with my information and renamed existing ones with names of my tables, i still had a sheet like 'Sheet 4', that was blank and i forgot about it. After i deleted it, everything started to work.

from flask-excel.

Any trace back for further diagnosis?

from flask-excel.