Why can't I resettle these pops?

When trying to resettle a pop to a different planet I get a message saying "Species Rights for Pop does not permit residence on this planet". Core worlds are allowed for all species.

What can I do to get this pop resettled?

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In the Stellaris menu "Policies and edicts" check two settings:

• Is the resettlement allowed
• Who can live on the core world

The first option is straightforward: if the resettlement is not allowed, you can't force pops to move to the other planet. The second is more tricky and easy to miss, but basically it has three options for your planets that are your under your direct (as not placed in sector) words:

1. Citizens only
2. Citizens and slaves
3. All species

Change this setting accordingly to your wish to allow pop resettlement.

Please also note that allowing the forced resettlement will upset your egalitarian faction.

Another possibility is the habitability: please check can the pop you are trying to move can actually live on the destination planet. I believe you can't move the pop if the destination habitability would be 20% or lower. Species that started with Gaia world (perfect world) preference cannot be move to any other types of planets (but they can live on habitats and ring worlds).