Could not find approvers or the permission is missing for order 00002030 placed by employee ?

hello experts, I have assigned appropriate permission and approver to my b2bcustomer.Also permission is assigned to Approver. But when the order exceeds threshold ,then Approver is unable to see order in his account. ? below is the b2bcomment related to order: Could not find approvers or the permission is missing for order 00002030 placed by employee.

any suggestion is welcome?

Regards, sid