Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
no need to install any add-on, I got this issue recently and as OP of this tread could not find a way to enable that option, so I figured it out (MS support is leaning from customers how to fix their product :) ) the needed link did not opened anything for me, but I fixed all issues by enabling Compatibility settings in IE, select "Use MS compatibility list" and then the same page reopens, but this time it will have check box.
have fun!