What version of OctoPrint are you using? There are some issues with 1.3.9 rc1 and rc2 that are being debugged presently. If you are using 1.3.9, I recommend either disabling Octolapse, or using the software updater to change OctoPrint to 1.3.8. If you are using 1.3.8 and everything is working EXCEPT that Octolapse is still reporting that it's waiting for the print to finish, that is probably a UI bug of some kind. Let me know if that's the case so I can figure out what's broken!
Regarding the built in timelapse tab, yes the completed renderings end up here if you have the 'synchronize with OctoPrint' rendering option ticked. Otherwise you have to download the file manually from the pi (big pain, I hope to add a file browser to Octolapse soon).
Please let me know if you need any additional assistance!
Edit: Changed 'synchronize with Octolapse' to 'synchronize with OctoPrint'