Ayush B. can you provide the Webflow read-only link so I can take a closer look?
In most cases, this is happening because there are existing duplicated classes within the project - regardless if class sync is turned on, you will have to clean your project of any duplicate classes before class sync will work properly.
In other cases, if this was done correctly, and you are still having issues, try some of the troubleshooting tips found at the bottom of this article.
Here's a doc that goes into more detail about how to prevent duplicate classes:
https://www.relume.io/resources/docs/how-to-fix-and-prevent-class-duplication-in-webflow
If you've tried these things and still running into issues, please do reach out and I'd be happy to take a look.