You should follow the instructions in the article and make sure that you are choosing the right page in the dropdown:
https://support.wix.com/en/article/linking-to-a-dynamic-page#linking-to-an-anchor
If you are still experiencing the issue when following the article - you can submit a ticket so we can take a look at your Editor:
https://support.wix.com/en/article/contacting-wix-customer-care-for-support
