Welcome to the Shopify Community and thank you for sharing your question.
When using Shopify Payments, our financial services team may do checks on accounts and take a look at the overall well-being of a store. Based on the message you shared, this looks to be a standard review and your customers are still able to checkout on your store.
This review can include reviewing requested documents, how soon orders are fulfilled, and any high-risk orders that may be placed. This helps our financial services team determine our merchants continued eligibility to use Shopify Payments. You can view all this and more information on our Shopify Payments Terms of Service page.
If our financial services team requires additional information, they will contact you directly via email with information or the next steps. If you have been in touch with our team regarding the hold on your account, the best place to get more information would be to reply directly to the email they have sent as they are the team that would handle this. If you’re unable to locate an email from our team, I encourage you to create a support request through the Shopify Help Center.