If you are getting bruises along your ribcage, that tells me you are throwing yourself into your invert instead of going upside down in a controlled manner using the abs and arm strength. You got lucky a few times and managed to hook the pole to get upside down BUT now it isn’t working because you don’t really have the strength built up yet to be able to do it consistently. Not to worry, with time your strength will increase and you’ll be inverting like no one’s business! But until you get to that point I would recommend doing some strengthening exercises and inversion preparation moves instead of throwing yourself into it and risking injury. Check out the thread titled "Am I ready for an inversion?" under pole moves in the forum, it will be at the top of the page.
Fleur