Portfolio assignments control how customers are grouped and which users see them. To prevent unintended changes, changing them is restricted by role and permission.
If you are unable to change a portfolio assignment, it is most likely due to your role or permissions.
User Roles and Permissions
Admin
Admins have full access to portfolio management and can always change portfolio assignments.
Member
By default, Members can view portfolios but cannot change portfolio assignments.
An Admin can give a Member control over this by switching on the Add customers to portfolios permission, without changing their role.
For more information on role levels, see Levels of User Permissions.
How to Give a Member Portfolio Access
Go to Settings → Users & Permissions → Users.
Click on the user you want to edit.
In the permissions section, switch on Add customers to portfolios.
Save your changes.
Only Admins can change this permission.
What You Can Do if You Are a Member
If you need a portfolio assignment updated, you can:
Ask an Admin in your organisation to make the change.
Ask an Admin to switch on the Add customers to portfolios permission for you.
Ask your company Admin to update your role.