One solution might be to have your list have two columns, one called Assignee for the person responsible for the task, and another column called Task Status.   Each time an assignee completes a task their status column is marked as completed though the Update Item action within the workflow.  This way you could create a Site Workflow and have it run daily on a schedule to look through all the people who have no yet completed their task and notify them.   This can be done by using Query List with a filter on the TasK Status and then a For Each to loop through your Collection.

Thanks

Mike

Instead of doing a list, you can create a different flexi-task for each person. You can set the flexi task up to send reminders after x number of days. The reminder shouldn't run for those who have completed their task. You can use a list to determine the group name. Use that group name in the flexi-task. Query the list for those groups and put them in a collection. The collection variable can be used in the flexi-task.

Any thoughts on these responses Chetan Patel​?

‌ which method did you use in the end?