We reviewed the Dec 2020 similar topic and followed the troubleshooting steps there to no avail, so am opening my own topic to be able to send information privately to support.
My site is being redesigned in WordPress by a group of students. I added their development url as the staging site license. When they had trouble validating the license, we found this help info and attempted it, but it was not helping:
Support topic: License validation X-Theme
Referred to this doc for troubleshooting:
Problems with Product Validation | Themeco Docs
I will sent the site url and an admin login privately.