do i need to pay again for the latest version,
It depends on what kind of license you currently own. I couldn't find your license.
The update itself won't "fix the problem" by itself. But it has some improvements, including an error messaging window, which would help you identify some of your scene problems. Here they are:
1. Gamma settings are wrong. Please always use these settings when using Corona:
https://coronarenderer.freshdesk.com/support/solutions/articles/50005156472. The glowing parts of light fixtures should be using Corona mtl with self illumination instead of CoronaLightmtl, see:
https://coronarenderer.freshdesk.com/support/solutions/articles/50005156033. There are some portals placed incorrectly - they should cap the window holes. Some portal(s?) was also intersecting with the wall. See:
https://coronarenderer.freshdesk.com/support/solutions/articles/50005016604. "mirror001" object - the light is intersecting with the mirror - this should be fixed
5. The most noisy area is caused by environmental light entering through the small window on the other side of the room - you need to reposition the portal in it so that it strictly caps the window, it helps a lot. Another idea would be to slightly decrease the intensity of skylight.
6. Setting sampling to GIvsAA: 16 , LSM: 4 seems to be an optimal solution, although it might require additional tweaking.
I am attaching a comparison of your original scene, and the "fixed" version. Also a 5 minutes render which looks pretty ok, so if you allow one hour or so for the image to bake (on similar system) then it should look fine.