It's right. Both are right despite when we speak is common to say "l'accettate" because it doesn't sound good to ears because of the double "a" too close.

Probably the only case when you hear "la" is because you want to emphasize the object.

Por quê não o aceitam esta resposta? Perché non lo/ la accettate questa risposta?

in any case use l' that is always right xD.