Are you using a thin wall socket (or standard cheap plug wrench) ??
Anything else won't fit.....and sometimes even the thin wall socket won't on some models.
If there really IS a washer or grommet around the insulator part of the plug, you're gonna have to get it out somehow.
I wonder if it could be part of an old plug wire boot that broke off ??
Hi I’m new here and trying to get the spark plugs out where can I buy a factory 18mm spark plug tool and is there only 2 plugs because that’s all I see