Genesys webhook signature verification failing on replay

The X-Genesys-Signature header isn’t matching my HMAC calculation. I’m using the raw POST body and my secret, but the result is always different.

sig = hmac.new(secret.encode(), body.encode(), hashlib.sha256).hexdigest()

Genesys sends the signature as sha256=abc123. Should I be stripping that prefix before comparing, or am I hashing the wrong payload?