Neocities.org
Still awaiting a response from Neocities, but in the meantime I have found a solution to work for all users. I've made a slight modification to how the URLs are structured when embedding your chats. Please, visit the dashboard, click the edit icon on your chat, and copy the new link to your chat. This is the new embed link and should work 100% for all users permanently!
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--> https://iframe.chat/dashboard <--