Broken HTML has been detected in your theme’s sections/main-page.liquid
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file. Check that there are no missing or extra HTML tags present.
If you haven’t made changes to this code, contact support
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for help resolving the issue."
The biggest mistake for this to happen is probably the description. You try to delete the description of the page and then check in the editor to see if it is due to it, then check each part. If it is because of it, please check your html structure again, is there a closing </> tag missing?
If you feel like my answer is helpful, please mark it as a SOLUTION. Let me know if you have any further questions.