To register your TS12 to your account, go here: 
https://www.auran.com/planetauran/SN_Enter_Serialnumber.php
The merge function has been broken from the start of TS12. They aim to fix it in the soon[SUP]tm[/SUP] to be released Service Pack 1.
Although it sometimes looks as if merging smaller sections works, some stuff on the inside gets broken and as a result you end up with tracks no longer movable and other strange kind of things you cant explain... until you remember using the merge function.
Avoid merge like the plague until they fixed it.