ssh works but not scp - Permission denied (publickey)

I am able to ssh into a remote server

ssh -i "C:\Users\kong\Documents\prl.ppk" haziq@10.0.1.111

but not able to scp

scp -i "C:\Users\kong\Documents\prl.ppk" kong@10.0.1.111:~/home_nfs/kong/script/train.py "./script"

but get this message

Load key "C:\\Users\\kong\\Documents\\prl.ppk": invalid format
Permission denied (publickey).

How do I fix this?

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