The person embarrassed by a compliment may be learning how to receive attention kindly.

Deflecting praise is usually a skill gap rather than modesty. Nobody teaches you how to be looked at approvingly, so the reflex is to argue, joke, or hand the credit somewhere else, and all three quietly reject what the other person was offering. Learning to take it is a genuine thing to learn, and it takes practice like anything else. Awkwardness in the meantime is not a character flaw.

The next time somebody praises you, say thank you and nothing more. And if you are the one giving it, keep the compliment short and specific so it is easier to accept.