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1. User is not assigned to a Location or Case sharing group - without a Location or Case Sharing Group associated to the mobile user, CommCare is forced to set the ownership to the user. However, setting the ownership to the user will automatically prevent the case from being shared, so CommCare prevents this behavior from happening automatically.
   1. Solution: assign the user to a Location or a Case Sharing Group
2. User is assigned to more than one case sharing group and/or location - considering that there are many options available, CommCare is unable to decide on who should be the rightful owner, resulting in that same error being thrown. This also applies if the user is assigned to one Case Sharing Group and one Location when the Organizational Level is set to Own Cases (see more in Setting up Organization Levels and Structure).
   1. Solution: There are two potential approaches here. You can change the configuration of the user so that they are only assigned to a single Case Sharing Group (see more in Mobile Worker Groups) or Location (see more in Assigning Mobile Workers to a Location). Alternatively, you set the ownership manually within the form (see below).
3. User is assigned to a Location that can't Own cases - in this scenario, CommCare sees that the user is assigned to a Location that, according to the configuration of the Organization Level, can't own Cases.

   1. Solution: There are two potential approaches here. You can change the configuration of the location to allow it to own cases (see more in Setting up Organization Levels and Structure), or you can set the ownership manually (see below).

4. User is assigned to a Location with child Locations and View Child Data is Enabled - this is a more complex problem to solve. In this case, it typically appears that the users are correctly configured, and that each one is assigned to a single location. However, since the user has access to data in the child locations as well, the child locations are also considered valid candidates for case sharing, similarly to if the user was actually assigned to multiple locations as outlined above.
   
   
   In this example, we can conclude that Nurse should be able to see cases from their CHWs and also to have their own cases. The error would occur when Nurse tries to create a new case, however, the app should work fine for CHW 1 and 2.
   
   1. Solution: In this case, usually the only viable option is to set the ownership manually. Of course, you could turn the View Child Data option off but this would most likely go against the workflow of the app.  

Setting

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case ownership manually 

So, at this point it's safe to assume that you have exhausted all other options and decided to set the ownership of the case manually. First, you need the ID of the owner, this can be achieved either by having the user selecting a Location or a Case Sharing group from a Multiple Choice Lookup Table question or some calculation that returns a single ID. Next, you need to instruct CommCare to assign the ownership based on that ID, for that you have to set the case property owner_id in the Case Management section of your form. Find more information about this process in Assigning Cases to One of Multiple Locations.