Continuing the discussion from Theme not validating, Cornerstone has no validation option:
You were correct about the data being corrupted. The characters were unescaped inside postmeta table _cornerstone_data row.
so I took the following steps:
1- restored fully functional backup from 7th January
2- cloned the website to staging /dev2
3- updated manually cornerstone on /dev2 (manual update via FTP as described here https://theme.co/apex/forum/t/setup-updating-your-themes-and-plugins/62)
4- cornerstone is working and all elements show - manual update successful
5- tried to re-enter license key - didn’t work - and now cornerstone doesn’t open…
I still cannot validate cornerstone, please help