Repeatdata on table shows on design but not on Web preview

Please check:

A cross-origin resource sharing (CORS) request was blocked because of invalid or missing response headers of the request or the associated preflight request .

To fix this issue, ensure the response to the CORS request and/or the associated preflight request are not missing headers and use valid header values.

I get this

I thought Wappler handles everything…h…e…l…p…

So please provide more details and/or screenshots of what you are doing on your page exactly. Also a screenshot of the error message you are pasting.
The info you are providing is not enough.