i get a error from the search console

Hello,

Thank you for getting in touch and I am extremely sorry about the trouble this might have caused.

There are a few things you must check for in order to see why an of your pages/posts aren’t getting indexed.

1. Make sure the post is not selected as ‘noindex’ in WP > Posts > Your Post > Advanced Tab in Rank Math.
Screenshot:

2. Ensure that the noindex is not selected for Global or Posts meta:

3. Check the sitemap settings and check if the posts & pages are setup to be included in the sitemaps:

As for your Old site indexing, you should redirect all of the URLs from your domain to the new domain to pass the the indexing data to your new site. If you just want to clear the old domain data from Google completely, you should consider using Google option for URL removal: https://support.google.com/webmasters/answer/9689846?hl=en

That said, please note that it is completely upto Google if they want to index or not index your website. So, if you haven’t willingly or accidentally made your posts noindex and Google still isn’t indexing your page – it means that either Google doesn’t want to index or hasn’t crawled your page yet because it hasn’t allocated that much crawl budget to your website.

Please check this website for more details.

Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.