It is possible that the workbook is corrupted in which case the following might not work but worth a go.
Press ALT + F11 to open the Visual Basic Editor, Insert > Module. Copy and paste in
Dim cht As ChartObject, ws As Worksheet
Application.ScreenUpdating = False
For Each ws In ThisWorkbook.Worksheets
For Each cht In ws.ChartObjects
.Height = 200
.Width = 200
Application.ScreenUpdating = True
then close the VBE using the X. Tools > Macro > Macros, highlight ResizeCharts and click the Run button. If successful this will resize every embedded chart to 200 x 200 pixels.