User cannot shipping

When a registered user cannot shipping is because he hasn't an adecuate permission or ROL.
For add permission  to user , use Commercial responsability,then  go Roles and permissions definitions | Permissions
In Shippping execution permisions form you can add or modify row with  username and appropiates permissions.
See screen below for more details:

User cannot retrieve OPM inventory information

When a registered user cannot view OPM inventoty is because he doesn't OPM organization permission. 
For changing it , use OPM System Administrador responsability and  go Setup System | User Organization.
You have to give organization permission for each user as you see below: