The product is automatically locked after a set amount of installs (each Automatic Online Activation counts towards that number, and you've reached that number now). This is a security measure preventing the product being installed by mutiple users on multiple computers if your Order Number is accessed if you get hacked.

To unlock your product: https://www.captainsim.org/forum/csf.pl?num=1541289733

Note. A Manual Offline Activation counts as a single activation, but can allow many installs on the computer that the Code and Key are created for avoiding the locking of the product for much longer period. Each Code and Key is different for each computer, so if you upgrade your computer, you will need to create a new Code, and recieve a new Key if you install it using Manual Offline Activation again.