Hi @BarakS ,
Actually, we have faced similar issue with PowerApps Portal last week. Now, I think this issue has been fixed.
As an fixed solution, please take a try with the following fix steps:
1. Go to "Administration" of your PowerApps Portal as below:

2. Within the opening "PowerApps Portal Admin Center", go to "Portal Details"-> "Change Portal State", change the State from "On" to "Off", then click "Save" button to save your changes.
3. Then change the "Change Portal State" from "Off" to "On", click "Save" button again, save the changes.
4. Edit your Portal again
In addition, you could also consider take a try to re-start your Portal, then check if the issue is fixed:

Please consider take a try with above solution, then check if the issue is solved.
Best regards,