Many company HRs think that they have some supernatural powers and can do anything with an employee,especially with a left employee. It is true that in order to make transfer possible, the previous company should mark the employee "exit" from their records. If they do not mark a left employee exit, they are supposed to pay contributions in respect of the left employee. It is okay that there will not be any contribution to PF or PS since there is no wage payment for the period in question, but keeping an employee as member even after his exit will be viewed by the EPFO very seriously.
In this case, as online transfer has been done and only approval by previous employer is pending, it should be presumed that the previous employer has done Exit of the employee, otherwise, you will not be able to do the transfer request.
If the previous employer is not approving the same, you can generate another transfer request with APPROVAL by PRESENT employer so that without previous employer's approval you can transfer the funds.