You are not using a Paid Business Manager! If you buy a Business Manager, your WhatsApp account will be blocked as the WhatsApp Business Name and the Facebook Business Manager will be of different businesses.

The Facebook Business Manager is atleast 1 month old and it has -

Your business should be a Registered Business and you should have registration docs, that contain Address as well as the Legal Business Name.

Your legal business name should be written in the footer of your website or anywhere else, such that it can be easily found by searching it via "Ctrl+F" - if it is not there the verification will be rejected

Go to your Business Settings and select your business.

Go to Security Center

If the “Start Verification” button is grayed out or not visible, follow steps in this article to become eligible.

Under the "Verification" section, click on the "Start Verification" button.

Fill in all the details as they’re mentioned on your Business Registration Document.
​Note: You need to have documents that contain your Business Name along with the address and phone number you enter here.

When it asks you to select your business, always select "My Business Isn't Listed"

Always select email as your preferred verification method and make sure you have an email with your website's domain.

When Facebook asks you to upload a document, upload a copy of your Business Registration Documents and make sure it has both your legal business name as well as the address you entered in the beginning.

Complete the verification step and enter the verification code that you will receive and click on the "Continue" button.