Karlie here from the Shopify Guru Team! If you've transferred over your domain from Wix to Shopify, then you should be able to renew your domain from within your Shopify Admin. You're going to want to follow these instructions:
You can also use our step by step guide, here, to help you with renewing your domain or disabling auto-renew in the future.
I hope this has answered your question. If not, or if you have any further questions please let me know. I will be happy to help!
Karlie here! Did you transfer your domain by following this guide? Or did you simply point your domain to your Shopify store. If you've pointed your domain then that means that your custom domain URL isn't hosted by Shopify. Pointing your domain would mean that you went into your old domain provider admin and you changed the DNS settings to be pointed at your Shopify store, pointing your domain looks like this. How long ago did you make those changes? If you could send me any additional details you might have - then that would be helpful!
We created a guide on how to transfer domain to Shopify, you can read it here. Please make sure you followed all the step in the article. Hope it helps!