2) according to your screenshot you are calling properly oktech_get_grades since you get the expect answer in ULI Test course and Greening Your facility Management Operation, that is an instance of class gradeRecord (as defined in wspp/classes) with course id number in field itemid , but unfortunaltely 0 as grade...
3) make sure you are using the latest from https://github.com/patrickpollet/moodlews . Some issues were recently reported against Moodle 2.4 see https://moodle.org/mod/forum/discuss.php?d=226161 and https://moodle.org/mod/forum/discuss.php?d=225924
4) you may try enabling debug mode in OK Tech in site administration settings . Then you will find in your moodledata directory a file named debug.out with a lot of var dumps of intermediate PHP variables and another one named wspp_db_errors.log that records specific database errosr that starts to appear more and more often with successive Moodle versions.