Mac auto login - window is grayed out.

ok. then you can try starting your mac into safe mode. please see this article: Start up your Mac in safe mode - Apple Support.

if the issue does not occur in safe mode, run the system that way for about 10 minutes. then restart normally and see if the issue is resolved.

if it's not, i'm thinking you should download and run the free version of EtreCheck so we can see if you have some software installed that is causing your issue. make sure you give "full disk access" to etrecheck. read how to use it by reading Using EtreCheck. if you need help interpreting the report, you can see how to post the report here by reading How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report. and it automatically obscures sensitive things (like serial numbers) so you don't have to worry about sharing the report here.

did you unlock the panel by clicking the padlock then entering your admin password when prompted?

everything is greyed out when locked.

once unlocked, the settings are accessible.