Login Error after upgrade!!! Please help

[kobis]

After upgrading from 8.1 to 8.6 i got this Error:

ERROR: Exception
Cannot find a key for product "Plesk"

0: auto_prepend\auth.php3:41
iskeyprop(string 'demo')
1: auto_prepend\auth.php3:41


Please advice. Is it related to license? Do i need to buy a new license for a minor upgrade?

 

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Nice to see SWSoft/Parallels are on-the-ball! typical...