If the IP address that you blocked is still tracked, you may need to check if you added it in the right way.
Always use a full IP address that you want to exclude from traffic. Even when you use Mask IP addresses or Collect data using a 30-minute cookie or Collect data without using cookies, add a full IP address. Piwik PRO will exclude the address before it masks it.
You can also use the wildcard like 54.217.*.* or 54.217.240.*.