You need to check if wp_bp_cohort_info table is created in the database.

If not, then fire the below mentioned query in phpMyAdmin

CREATE TABLE IF NOT EXISTS wp1i_bp_cohort_info ( ID INT( 11 ) NOT NULL AUTO_INCREMENT,COHORT_NAME VARCHAR( 50 ) NOT NULL ,MDL_COHORT_ID INT( 20 ) ,PRODUCTS VARCHAR( 100 ) ,COURSES VARCHAR( 100 ) NOT NULL ,COHORT_MANAGER INT( 10 ) NOT NULL ,INCOMP_ORD VARCHAR( 50 ) DEFAULT NULL ,SYNC TINYINT( 4 ) NOT NULL DEFAULT '0',PRIMARY KEY ( ID ) ,UNIQUE KEY cohort_name( COHORT_NAME ));

Once this is done increase the table size of this column: cohort_name
You need to change the value from 50 to 190/250.

Try purchasing the product again using Bulk Purchase plugin and let us know the results here: edwiser@wisdmlabs.com

This issue is caused due to lack of necessary permissions for the user mentioned in wp-config.php, you need to check if the user has permissions to create and edit the table in the database.