"Hi, are you okay?"

Translation: Szia, jól vagy?

[Bawskyy]

Can't hogy vagy be used here instead?

[Findil]

The meaning isn't exactly the same.

"Hogy vagy?" (lit. "How are you?") asks the person to describe their current state of mind/health in general, while "Jól vagy?" (lit. "Are you alright?") simply asks if they're fine or not.

[Bawskyy]

Brilliant! Thanks!