Black list IP

Well, I certainly do not know, the current supported version of the code that powers the Sucuri Scanner has no such feature of IP blacklisting. You are probably confusing this plugin with another one, or are using a very-very-very old version of the code that is not supported anymore (please update the plugin if this is the case), or the blocking that you are getting is not from the plugin but from CloudProxy [1] in which case you can simply go to the WAF dashboard [2] and de-blacklist the IP addresses that you want.

[1] https://sucuri.net/website-firewall/
[2] https://waf.sucuri.net/?settings&panel=whitelist