...
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.
Solution: assign the user to a Location or a Case Sharing Group
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 oneCase Sharing Group and one Location when the Organizational Level is set to Own Cases (see more in Setting up Organization Levels and Structure).
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 https://dimagi.atlassian.net/wiki/x/YzPKfw). Alternatively, you set the ownership manually within the form (see below).
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.
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). You will need to ensure that all cases created within the form settings Form Settings have an owner_id property set, including any child cases.
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.
...