I've stripped my code all the way down and am left with these simple models:

models.py

class Member(models.Model):
    property = models.OneToOneField(Property, on_delete=models.CASCADE, blank=True, null=True)

class Property(models.Model):
    ....

And this very basic admin for Members:

admin.py

class PropertyAdmin(admin.ModelAdmin):
   pass
admin.site.register(Property, PropertyAdmin)

class MemberAdmin(admin.ModelAdmin):
    pass
admin.site.register(Member, MemberAdmin)

While logged into the admin as a superuser, as expected on the Member admin page I see a dropdown to choose a Property model. When there is already a Property model selected, the usual pencil icon to edit the selected Property model is faded out, so I cannot click on it. How can I activate this icon so that I can get the usual pop-up to edit the related Property from this Member page? I can't figure out what I am missing.

Thank you!