Any ppt file downloaded from internet is usually remained blocked and hence Presentation cannot be opened

Method One

If you've found that any ppt(x) file does not open after being downloaded, it's likely that MS Office has blocked the file for security reasons.
You must unblock the file to open it:

• Open file location where you have downloaded the file
• Right-click the file and left click click on Properties.
• In the Properties dialog box, look for an Unblock button near the bottom right corner; once you get it, click Unblock, then click Apply, and then click OK.
• Now you can open the file as usual.

Method Two

You might want to open the ppt(x) file directly from the download dialog box, in this case you have to allow your MS Office to be able to open any ppt(x) file without blocking it. To do so :

• Start PowerPoint
• Choose File then Options
• Click "Trust Center" on the left, then click "Trust Center Settings" on the right
• In the Trust Center dialog that opens, click "Protected View" on the left then "REMOVE" the checkmark next to "Enable protected view for files originating from the internet" OK your way back out of all open dialog boxes.
• Now you can directly open any ppt(x) file; any file you download would be "unblocked" by default.