From looking at the code way back i notice this plugin requires you do one of two things:
1. Give the full path to the file. If its a directory then the full path to the directory, postfixed with a "*". e.g. /home/hosting-username/blog/wp-content/uploads/wpcf7_captcha/*
2. Add a "*" wildcard at the very beginning of each relative path. But if the path is for a directory you will also need to postfix another "*". e.g. */wp-content/uploads/wpcf7_captcha/*
Notice the use of "*" wildcard at the beginning and end above. For directories you want to make sure to use the "*" at the very end. However, to ALSO use relative paths you would also need to use a "*" at the very beginning too.
This is why your first full path didn't work -- you didn't include a "*" at the end. And the other two paths (relative) were missing "*" at the beginning.
So in summation either of the following would now work: