Whatsapp doesn’t download on new phone

If you still have the old phone with all its data you can open Whatsapp, go to the settings, chats, and do a backup to iCloud. You may have to pop the SIM back

Then on the new phone, uninstall Whatsapp if the app is there then re-install Whatsapp. It will offer you to restore the backup

WhatsApp is not an Apple product. Contact the app developer here --> App Support or WhatsApp FAQ  Or Restoring your chat history - WhatsApp FAQ or Contact WhatsApp

WhatsApp Business is not an Apple product. Contact the app developer here --> Developer Website  or App Support  or WhatsApp business products - WhatsApp FAQ

How did you do the transfer?

From which device did you do the transfer?

Was WhatsApp Data on iCloud?

During transfer from an old devices Apps are never transferred only the App data gets transferred. Apps don't transfer from iPhone to iPhone, only the app data along with app links to the App Store gets transferred.

After the transfer is complete (Quick Transfer, iCloud, or iTunes) depending on the internet speed all apps will get downloaded from the App Store automatically. If an App does not exist anymore in the App Store or the iOS version is not compatible with the App then the App data that is transferred cannot be accessed any further.

With the limited information that you have provided, It is hard to even guess the problems faced by you. 

You may get faster and better responses to your query by --> Writing an effective Apple Support Commun… - Apple ...

Apps & Settings --> Apart from the Apps following will also not get transferred between devices

1. Content from the iTunes and App Stores or PDFs downloaded directly to Apple Books
2. Content synced from iTunes, like imported MP3s or CDs, videos, books, and photos
3. Data already stored in iCloud, like iCloud Photos, iMessages, and text (SMS) and multimedia (MMS) messages
4. Data that are synced to an email account such as Google, iCloud, AOL, Exchange, Outlook, Yahoo, or any Other email client server that supports contact synchronization. e.g. Contacts, Reminders, Notes, Calendars
5. Face ID or Touch ID settings
6. Apple Pay information and settings
7. Apple Mail data
8. Apple Music