Please clear your browser's cache. Sometimes, when copying and pasting between multiple windows in browsers there can be extra unseen HTML that can cause issues. To rectify the HTML error, can you try and follow the steps below?
Copy the text/disclaimer.
Access the webinar disclaimer again. If any old text remains in the field, clear it out and ensure there are no spaces at the beginning or end of the text.
On Windows, paste the text in using (Ctrl + Shift + V). This will paste in the text without formatting. On macOS it is (Command+Option+Shift+V).
Kindly click on Accept solution if this response has answered your query.