Sorry for the delay in answering.
1/ I’ve disabled Advanced Layout for Cart/Checkout layout via Theme Options. The checkout button works now.
Please provide FTP access, so I can pass the problem to our dev team.
If you do not know how to create FTP, your hosting provider should be able to assist you.
2/ Could you record a video of the problem?
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.