Unable to add a datatype to an imported data model

[CazFaz]

Hi,

Can anyone help please?
I've imported an existing database into EA because I want to model some changes.
I've been able to add an additional column to the field but can't set a data type - the drop down list is empty. All the other elements have a data type so it really does stand out that this one is missing.

I may well have the config on the diagram wrong but if anyone can help it would be much appreciated.

Thanks,
Caz