Workflow Lead Creation - Want to assign the Lead to the person whom he reports to at the time of creation

I am struggling for almost a week to find the solution for the problem, it would great for someone to step in and help me to solve this problem

I have created a simple workflow (Runs always and on NEW Records) which has NO condition but has one action , The action is Modify Record Lead (the one which is created). I have added a new Field, whose drop value is “Assigned To” and the association is “Field” and the value selected is “Reports To”.
The assigned To column of Lead never changes to Reports To column as mentioned in the user. Please help, following is additional information.

I have security groups and this issue is within a specific group, no one person from one group can have the lead assigned to other group.

If I use the association as Value and hard code the reporting to a specific user, then I see that the assigned to column of Lead changes to the one I have selected in workflow.

Appreciate if anyone can help me on this issue. Thanks in advance …