You need to unblock the downloaded file using the steps below.
Locate the File: Find the downloaded $\text{.chm}$ file on your computer (e.g., in your Downloads folder or on your Desktop).
Open Properties: Right-click on the $\text{.chm}$ file.
Select Properties from the context menu.
Find the Security Section: In the General tab of the Properties window, look for the Security section near the bottom.
Unblock: You will see a warning message like:
"This file came from another computer and might be blocked to help protect this computer."
Click the Unblock checkbox or button next to this warning.
Click Apply, then OK.
The $\text{.chm}$ file should now open correctly with all content visible.