Search API module help – calculated fields not searchable/indexed?

Hi, I have installed and set up the Search API module and it is mostly working.

I only want to be indexing and searching specific fields, so in my index field management I have removed ‘Rendered HTML output (rendered_item) ‘ and instead added all the fields I do want searchable, including ‘title’ and ‘field_specification_text’, all set to type ‘fulltext’

I’ve run my index and can successfully retrieve content that has a partial match with the title.

I’m have no luck at all getting any matches against ‘field_specification_text’, It appears to not be indexed at all.

Now the complexity is that ‘field_specification_text’ is a computed field that effectively holds a string list of all my related entity taxonomy terms associated with the content.

What I’m after is to be able to find a record by searching for its taxonomy term… either by getting this calculated field work around going, or even better, if there is a way to index the related entity terms against an item OOTB using Search API.

Thanks for taking the time to view my issue!

(fingers crossed for a solution)

Drupal version: