Issue
Unable to maximise the opened Excel Worksheet (See attachment)
Issue
Seems to be a compatibility issue between Excel 2013 & Excel 2010
Solution
Review > Changes > Protect Workbook, and uncheck Protect Structure and Windows
Then maximise the window
Link
http://superuser.com/questions/135326/what-the-heck-have-i-done-to-my-excel-sheet-and-how-to-undo-it
http://www.spreadsheetsmadeeasy.com/excel-view-multiple-worksheets-at-the-same-time/