Whatsapp not opening for more than 1/2 seconds - either black screen or opens for just 1/2 seconds

Hello,

I bought my iphone 6 months back, but just today moved Whatsapp from Samsung Galaxy s7 to iphone XR.

I have moved my whatsapp from Android to Iphone using Dr.Fone App. Now on the iphone XR, when i click on the Whatsapp Icon, i am unable to open it for more than 2 seconds. However, the whatsapp notifications seem to be coming, and as soon as i click on them, it goes to whatsapp, and then closes automatically after a second.

Things i have already done:

1. Restored whatsapp again on iphone XR

2. Deleted Whatsapp and again downloaded new one from App Store.

3. Shut down the phone again and restarted it.

COULD YOU PLEASE HELP ME AS THIS IS VERY CRITICAL RIGHT NOW