In order to enable your Twilio number for WhatsApp, you will need to fill out Twilio's "Request Access" form with accurate and up-to-date information, including your Meta (Facebook) Business Manager ID.
The information must correspond to the company whose brand will be represented on the WhatsApp business profile. Providing incorrect information here can lead to delays in the onboarding process.
Below is additional information on some of the fields on the "Request Access" form based on frequently asked questions:

Phone Number: The phone number where the user or business requesting access can be contacted, not your Twilio Phone Number.
Email Address: The address where Twilio will reach out with the next steps once your account is approved for use of the Twilio API for WhatsApp in production.
Are you working with an ISV (Independent Software Vendor), SI (System Integrator), or third party?: Since Grid users are neither an ISV nor an SI, select No.
Company Name, Website, HQ Country: Your company’s information. To avoid delays, this should be the same company name used in your Facebook Business Manager account, and the same name that will be displayed on the WhatsApp business profile, once you go live.
Twilio Account SID: Your primary Twilio Account SID. To find your Account SID, log into the console click the “Home” button, and locate your Account SID on the top right on the page. If this is a Flex account, use your Flex Project Sid.
Facebook Business Manager ID: This is equivalent to a Meta Business Manager ID. You can find this ID by following this link, or logging into business.facebook.com > clicking “Business Settings” > "Business Info" > Look for the Business Manager ID. (More information about submitting your Meta Business Manager ID)
- "I've completed Facebook Business Verification": This is equivalent to completing Meta Business Verification. Learn more about Meta's verification process documentation.
- "I understand Twilio can modify my SMS/Voice URL and that approval is only for the brand submitted": Twilio may momentarily use your Twilio number’s SMS or Voice URL to register your number with WhatsApp.

Await pre-approval from Twilio

After you submit the "Request Access" form, you will receive an email confirming the form submission.
Once Twilio reviews your account, you will receive an email with subject "You are now pre-approved to use Twilio APIs for WhatsApp". This message will contain the next steps for you to follow for submitting your sender Profile and WhatsApp Message Templates.
Note : If your company has missing information or falls in a vertical forbidden by WhatsApp's commerce policy, Twilio may reject your submission. Final approval is provided by WhatsApp after you submit your sender profile (next step).

How to update non-grid account holders with notifications?

How to update non-grid account holders with notifications?