Issue is not with excel download. Few users unable to view the content( file content is blocked) while some users able to view. so i would like to know if something had been changed in pega recently with respect to security configuration of downloaded excel file especially access to content? because same users were able to view the content one month back.
can you try *saving* the Excel file (rather than directly opening in Excel); then renaming the file extension from 'xls' to 'htm' : and then take a look using a Browser and also a Text Editor.
[ The 'Export To Excel' feature available on PRPC Reports (and other places possibly) actually delivers a HTML file with a few extra EXCEL stylings , rather than (say) a Binary XLS file ; which is why you need to be careful NOT to open the file for this test - as Excel will render the format automatically to a native format as soon as you open it/save-it - and you'll lost the ability to check the contents. ]