There are two likely reasons for this:
When the form first loads, it defaults to a search range for the current month (it is necessary to scroll down the search options to find this). Changing the criteria from range to none will return all items waiting for approval.
The form is restricted only to show transactions associated with you. There is a setting in the FinOps Administrator that allows you to see or edit invoices for other users.
Go to System Control and select the security profile for the member to be changed.
Click Edit and click on the drop down for Invoice Register Approval (under Approval Options)
Toggle the field to the required setting - All Approvers or All Read Only, Edit Own.
Click OK to save the changes
Please note that this will allow all users in that security profile the access granted. for further assistance, please contact your FinOps administrator for more information.