Periodically I download from my bank a spreadsheet of my transactions. Recently though an update to Excel (version 16.0 as in Office 365) stopped these .XLS files from opening. Instead I see a blank page. To view the contents I must now right click the downloaded file, select 'Properties' and in the General tab check the 'Unblock' at the bottom. It's a pain, especially since Excel will still warn me that the file came from an external source and still ask me if I want to enable editing. It seems Microsoft use belt, braces (that's 'suspenders' in the US) and now a safety pin also.
I looked for a way round this and in an answer to an apparently unrelated question about slow saving of large Word files, I found a possible solution using a registry tweak. It worked and I now no longer have to unblock Excel files from an external source. Obviously, you should only do this with files from sources you trust (can I trust my bank?).
Note: The method to fix the issue will modify the Registry. Before you do this, make sure to back it up and understand how to restore the registry if a problem occurs. Please refer to this link: https://support.microsoft.com/en-us/kb/322756 How to back up and restore the registry in Windows.
Using Regedit, go to this registry key address:
If this doesn't appear to be present, you can create it. If your version of Excel is 15.0 or earlier - just change that to the appropriate number.
Double click the REG_DWORD: EnableOnLoad, set its value to 0 (zero) and restart the PC.
You'll now find you only get two warnings about external files instead of three.
Incidentally this same registry tweak will also help with slow loading and saving of large Office files.