Your listing is invalid and cannot be sent to moderation

Summary

I updated a previously published product by adding the Unity package version, as I’ve always done with my other products.
When I click submit for review, I get the following error message:
Your listing is invalid and cannot be sent to moderation

What type of bug are you experiencing?

Publishing

URL where the bug was encountered

https://www.fab.com/portal/listings/eb6e5674-3316-4eaa-b800-663cbf674730/edit

Steps to Reproduce

submit for review button

Expected Result

Product submitted for review

Observed Result

Your listing is invalid and cannot be sent to moderation

Platform

Chrome

Operating System

Windows 10

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Additional Notes

Please Help!