To fix ie error 504 error, just follow the steps given below:.
1.Click on Start up and select Control Panel.
2.Click View network status and tasks and when you enter, select Change adapter settings.
3.Right click on Local Area Connection and select Properties.
4.Select Sharing and make sure you won't tick Allow other network users to connect through this computer's Internet connection to disable connection, at last click OK.
To turn off add-ons
Open Internet Explorer, select the Tools button, and then select Manage add-ons.
Under Show, select All add-ons and then select the add-on you want to turn off.
Select Disable, and then Close.