Unfortunately as this is an extension to GMS, I can only support the latest versions of Spine supported by GMS itself.
For GMS 1.4 this is Spine v3.4.02 as detailed on the GMS 1.4 Required SDKs article. For GMS2 this is Spine v3.7.x as detailed on the GMS2 Required SDKs article (for GMS2 2.2.2+)
GMS2 v2.2.2+ added the functions in the extension natively into GMS2 itself, so it is no longer needed in versions of GMS2 later than that as the functions are now "built-in" and a native part of GML. This is stated at the top of the main extension page as a note.
Spine 3.3 was released in June 2016 - over 3yrs ago. Is there any particular reason you can't update to one of the recommended versions of Spine for use with GMS 1.4 or GMS2 as per those articles I linked above?
