Iodine, how are they prioritising internal candidates? They should either be advertising it internally first, so you never see the advert, or thereshould be a fair playing field within a pool of internal and external candidates, although tbf internal candidates often give better examples because they know the sort of situation you'll have had in mind when you drafted the question.
I'm interviewing next week for a post, 13 candidates, 3 internal. I've interviewed one of the internal candidates since we appointed her, for a promotion, and she made an utter balls up of the interview. Similarly I got my job as an external against an internal candidate.
Generally, if you don't need a degree to do the job, you need previous experience and to really give examples to show off your skills not just say "I am an excellent team player". For the post above, we had 74 applicants, but only had 20, max, decent applications, and we wittled those down with relevant sector experience. If you're applying and not getting interviews, or not getting through interviews, please do go back and ask for feedback from the shortlisting / interview panel - not from HR. They should be able to give you detailed feedback although sometimes it's not that you did anything wrong, only that someone else had more extensive experience and interviewers can't interview 30-odd people for a job so have to cut the applicants down to a workable number, setting some obviously good candidates aside as they do so.