:disabled
option is supported only by following selector types:
:field
:link_or_button
:button
:fillable_field
:radio_button
:checkbox
:select
:file_field
It can be used as:
find(:field, 'field_id', disabled: false)
This option is not supported by :css
that you seem to use.
With :css
you are expected to use css's attributes which is much shorter:
find('#field_id:not([disabled])')