How to unblock Excel ActiveX controls
A new Office update blocks ActiveX controls in Excel files by default.
A file that previously worked fine can suddenly become blocked after this update.
When opening, a yellow banner with the message "BLOCKED CONTENT: Trusted document settings have changed, not all content in this file is allowed to run. Review your Trust Center settings or contact your IT administrator." is displayed:
Or in other cases, a yellow banner with the message "BLOCKED CONTENT: The ActiveX content in this file has been blocked.".
And in some cases, you might also see an error 438 displayed.
To unblock the file, go to Excel Options (File > Options), then Trust Center and click Trust Center Settings...:

In ActiveX Settings select Prompt me before enabling all controls with minimal restrictions:

Click OK and close Excel.
