EndNote limit hit

Hi - I’ve looked but can’t seem to find an answer anywhere - so thanks in advance for any pointers.

I have an EndNote library with 21,000 references and around 9GB of PDF attachments. I’ve set up EndNote Web sync and wasn’t sure what would happen when the sync attachment limit was reached (I was hoping that some useful information on how to continue would be provided).

However, I’ve reached the limit and sync has simply stopped. Help!