Hello, Kestutis,
You do not need to activate bundled plugins using a key, and you can’t do it using the purchase code from the theme. As mentioned in our docs, we do not provide activation keys for plugins – https://www.8theme.com/documentation/xstore/plugins/activation-and-purchase-codes/ . Bundled plugins do not come with personal licenses independent of the theme you purchased, read here – https://help.market.envato.com/hc/en-us/articles/213762463-Bundled-Plugins
Kind Regards,
8theme team