how to delete .plist file

Try removing YouTube cookie. It will take a while for these cookies to show up.

Be patient.

Choose Safari > Preferences, click Privacy, then do any of the following

Remove stored cookies and data: Click Manage Website Data, select one or more websites, then click Remove or Remove All.Removing the data may reduce tracking, but may also log you out of websites or change website behavior.

Manage cookies and website data:

https://support.apple.com/guide/safari/manage-cookies-and-website-data-sfri11471

Delete com.apple.Safari.plist file

Empty the Trash.

Quit all applications.

Hold the option key down and click the "Go" menu in the Finder menu bar.

Select "Library" from the drop down.

Library > Preferences > com.apple.Safari.plist

Right click on it and select "Move it to Trash".

Restart and relaunch Safari.

If this doesn’t help, “Put Back” the com.apple.Safari.plist

Right click on the Trash icon in the Dock and select “Open”.

Right click on the com.apple.Safari.plist and select “Put Back”.

Select ”Replace” from the dialog when it appears.