Hi ChristianC,
Open your Local Vault, go to the website you are having difficulty with, select Vault is Open > Logins and select Options on the Current Site block at the top of the dropdown. From there select "Report an Issue with this site", fill out the form that opens and it will be reported to Norton. they will get bck with you if they are capable of fixing it. I have seen it take awhile in some cases to get it fixed - if it can be fixed.
Hope this helps!