When you see the "pending" state for an interview request it merely indicates that the request has been sent to the dev, not necessarily that the dev has read the request (he/she would have received an email notification about the request though). We have an agreement with developers that they are required to respond to you within 2 days of receiving the request.
The response will indicate whether the dev has accepted or declined the request. They are required to provide a reason for their response as well.
In the event that you have been waiting for a response for longer than 2 days then you are welcome to ping us at OfferZen. Your account manager at OfferZen will then request the relevant talent advisor (the dedicated team member dealing with that specific developer) to remind the developer to respond to you.