I'm afraid we would be unable to provide a credit for the monthly subscription as the trial is intended to determine if the platform will be the right fit for you and your business and not determined on whether or not the store is approved to sell on third-party channels such as Facebook and Instagram. Both channels require an active paid Shopify subscription as one of the requirements to use the channel. All other requirements for Facebook can be seen here, and Instagram here. That said, the approval process does not typically take too long as long as the proper settings, and requirements are met for both channels. You should be able to get through the approval process within the next 30 days before another invoice generates for your store.
If you're having any issues with setting up either channel please let me know as I'd be happy to help get that resolved.