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I have Multi Company set up with two companies. 

I have a user, set for both companies in Allowed Companies.

When her Current Company is set as Company A, she is able to create and save Quotations without problem.

When her Current Company is set as Company B, she can not create and save Quotations, it returns the error:

The requested operation cannot be completed due to security restrictions. Please contact your system administrator.
(Document type: account.invoice, Operation: read) 

This ONLY happens within Company B, and ONLY when a custom module is installed which has a few View and Model extensions.  

So what I need to know is, "account.invoice, Operation: read": where can I set this that it will be Read/Create/Write for both companies?  It must be set correctly in general, because it works in Company A, but I don't know if I'm missing a step to transfer (if that's the correct word) the rights to when the user is in Company B.

And/or: Is there some extra permission/code I have to implement in the custom module to allow the permissions to extend to a second company?