Error message on epub for ingramspark

Hi. After uploading my epub to IngramSpark, I see this message repeated multiple times:

(RSC-005): /OPS/body.xhtml: Error while parsing file: element “p” not allowed here; expected the element end-tag, text, element “a”, “abbr”, “area”, “audio”, “b”, “bdi”, “bdo”, “br”, “button”, "can…

Can you tell the meaning? I am wondering what I can do.

Thank you!

Solved. Thank you to my future self.

How did you solve it?