This document will help you get started with debugging ERP5. It will show entry points on how to find errors and provide answers on common bugs you may frequently run into. If this is the first time you are working with ERP5 as a developer, this how to will help.
The exception log will list all recent exceptions. Find yours and click on it.
Check the stack trace. It will tell you what script threw the error and why. Most of the times this is enough to find and remove your error.
First make sure you this is not due to some settings on a listbox you are viewing and that there are no blocked portal activities.
If you can rule out both, your records not showing up might be caused by your ERP5 user not having necessary permissions. Normally every user should have an assigmnent declared on the person_module/[your_person_id]'s Assginment tab. Assignments allow to declare security and viewing permissions. To debug, try creating an empty assignment, start this assignment and check whether the problem persists.
Should this not work try calling the following script on the respective person through the url.
Please also have a look at How to distinguish ERP5, Zope and Developer users in case you are having trouble accessing certain parts of ERP5 or the zope interface.