Hi there praneeth104,
Thanks for reaching out to the Apple Support Communities. Just to confirm, are you following the steps below from the following resource when attempting to lift a subject from the photos background: Interact with text and subjects in Photos on iPhone - Apple Support
Lift a subject from the photo background
You can lift the subject of a photo away from the background so you can copy and share it in other documents and apps.
1. Open a photo.
2. Touch and briefly hold the subject of the photo. When it’s outlined, do one of the following:
- Tap Copy, then paste the subject into an email, text message, or note.
- Tap Share, then choose a sharing option, such as AirDrop, Messages, or Mail.
If so, does this issue occur if trying to paste the photo into a message in the Messages app? If not, then this feature may not work as expected with other third-party apps.
For the best information on using this feature in WhatsApp, we'd recommend reaching out to WhatsApp support at this link here: Contact WhatsApp
We hope that's able to help.
Take care!