Hey! So sometimes artists are really busy. I just commissioned and they would go about a week without responding because they also had other commissions.
However, if it’s a very small artist that doesn’t have previous commissions I would be very skeptical and let them know that if they do not respond within another week you can go to Paypal, or whatever app you used, and claim that they haven’t reciprocated the deal. Although, I would give it a bit of time before doing this, and you want to k]let them know before doing so.