WhatsApp Business API numbers can get blocked, just like your WhatsApp Business App or normal WhatsApp number.

If 

Many WhatsApp users report your messages as spam
Or
Meta algorithms believes your messages are against the WhatsApp Business Messaging Policy⁠, the WhatsApp Commerce Policy⁠, or the WhatsApp Business Terms of Service⁠
Or

Your Business Verification/Security fails - your website is broken, your legal information doesn't match, or Meta suspected a security breach.
Then
Whatsapp will restrict, and eventually ban your whatsapp business API number.
The good news is, Meta does this in a phased manner (Restrict - Disabled/Banned) and warns you in many ways before banning your number. Unlike the surprise ban on WhatsApp business App or normal WhatsApp number.

Restrict
You may get a 1-3 day restriction on sending messages. Your delivery rate can also be throttled. In some cases, the restriction can be stronger - 5,7, or 30 day block on sending any message.

Disabled/Banned

Permanently disabled from using the WhatsApp Business API Platform, if corrective steps are not taken even after multiple warnings.
Your Quality Rating by Meta helps you monitor this risk. When the rating drops from High to Medium or Low, it means you are under radar. Start taking corrective measures right away.

In some cases, where there is evidence of a policy violation that causes severe harm to users - such as child exploitation, scams, terrorism, or the sale of illegal drugs, WhatsApp will immediately offboard these Business accounts. No warnings in such cases.

Meta keeps it fair by letting you appeal from Meta’s Business Support home. For a step-by-step guide to appeal to restricted or disabled accounts.