If you purchased a domain via Shopify, I recommend you to email directly to Shopify's Merchant/Technical support. They should assist you with the issue!
Contact page link: https://help.shopify.com/en/questions#/contact/email
Thanks for reaching out.
Did you purchase this domain directly from Shopify or was it transferred from another domain provider? Let us know as this context will determine the next steps to troubleshoot the pending domain.
Looking forward to your response!