The error you are facing is mostly occurred when there was an edit or mismatch between the code that the server rendered and the code what was shown to you. In my experience with Next.js, This error wasn't a major error it was just a small red icon at the bottom left because In my end this error in most of my project was because of an extension which used to do some edits on the client side html code leading to this mismatch. So I think you shall try from guest mode and check if any such error occurs or not. If it still occurs then you should possible look up to your layout file or any other relative files to this home page and then you shall also make sure you've properly setted up the mui according to the documentation with correct style links, e.t.c (https://mui.com/material-ui/getting-started/installation/)