If you have used elements in your work that you do not own the copyright to (such as elements from Canva), it's important to mention and upload copies of the license agreement (by printing the page to a PDF) allowing you to use it (e.g. https://www.canva.com/policies/content-license-agreement).
It can be wise to add some text in the "Additional Copyright Holders" box when uploading work, such as:
This will appear on your digital certificate as follows:
If you have used AI (Artificial Intelligence) to help create your work, we recommend uploading your AI command list which can demonstrate your human interaction, creativity and judgement.
If element(s) of your book or audiobook have been purchased for use in your book (e.g. photos, illustrations or music, we strongly advise you to upload a copy of the license agreement granted to you by the copyright owner, or a signed statement from the creator that you have the legal right to use it in your work.
Your digital certificate from Protect My Work could be rejected by these portals if you do not include all the relevant information and licences.