I received the following advice from WGT:
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There is a known issue with declining invites and we're working very hard to resolve it. Many players are having success by either using a different browser or by making sure that wgt is the only window/tab open in their regular browser. You can also send a message to the country club's owner and ask them to delete the invite.
If it is a country club invitation you can accept it and then remove yourself from the country club. If you have trouble removing yourself from the club, let me know and I can remove you manually.
If it is an unwanted friend invite you can accept it and then remove them from your friends list.
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So I accepted then quit the cc and that seems to have done the trick.