The taxonomy field in the Form UI will only find exact matches in the taxonomy terms.
Are you wanting to search using the text search box?
If so, note that the Search & Filter Pro Text Search field uses the standard WordPress search, so looks only in the Post Title and Content, and in only their ‘standard’ way. To help you control this better, on the form’s Advanced settings tab you will see 2 settings for Relevanssi (one of which is Relevance).
The documentation for this is here:
https://www.designsandcode.com/documentation/search-filter-pro/3rd-party/relevanssi/
You would need to install and activate the free Relevanssi plugin as well.
Then set Relevanssi up and build its index (make sure it is indexing the desired post types, custom fields AND any taxonomy that you want to search).