I have identical problem as many people had before - J51 slideshow installed with J51_Oxygen template (free one) has been set up but does not work

Unfortunatelly, you did not provide any solution nor fix description to follow it. I would prefer before to gain you temporary access to a site you to give a few advices of how to avoid most common mistakes installing the Oxygen tepmlate and its slideshow to get them working.
Thanks in advance, Anna