The portal is intended to show records connected to the user's table. But it is possible to show all records from a table, even those that are not linked to the logged-in user. To do this, you need to do the following:
Go to Portal Tables
Click on one of the tables
Custom Views section
Go to one of the Custom Views
Set Choose Records to Display > Show all records.
This will show all records regardless if they are linked to someone else or no one at all.