While indexing your website as Googlebot (choosing the User-Agent - Googlebot from the SEO tool), the result status code is 403 (permission denied).

This might be due to the fact that you are using a WAF (such as Cloudflare) that can identify that this was a fake Googlebot and not the real Google service.

In you want further details on the way Google verify their bots you can check the following article: https://developers.google.com/search/docs/advanced/crawling/verifying-googlebot?hl=en&visit_id=637816908286123780-2366646208&rd=1