QBCC decision not in my favour. Not sure where to go next - air con installation advice

hello!

so June 2023 I had to replace the ducted air con system in my house, fast forward to January 2024 and the system started dripping via the house and mould nicely developed around the outlets. Air con installer commented I was one of other customers experiencing this, did not offer help or return until QBCC came out a matter of months later.

QBCC decision closed without inspections. I already had reports from mould experts, air con professionals pointing out the error in installation and flaws they recognised, and discovered in replacing the system I had been downgraded without details - I want to cry. QBCC complaint let to a review of that decision, and again I was told there would be no decision to rectify.

This was in October 2024 and now its January that I have gone and serviced the air con, had mould people in to address what was visible inside the house...to be told what is installed is unrecognisable, doesnt meet industry code, needs to be replaced and STAT. All of this is like 10k and I want to weep at how unfair it is>

I'm not a builder, I work in a professional space no where near this industry. It doesn't make sense that you hire a tradesperson and then not even two years later the onus is on me to spend so much money to fix what has been clearly identified as their poor work? that QBCC didnt do anything to recognise this. That in the overwhelm of life I obvs didnt get onto the 28 day notice to lodge anything with QCAT and now Im lost.

I don't know what I should do. I don't know if I keep trying to fight to have this cost recovered under the home warranty scheme or surely his public liability??? I had thought as a consumer we have rights to buy services or products that are not defective.

Is there any point to my overwhelm? does anyone have any friendly pointers for me? Im so sad. My house was never broken and I regret deeply the decision I made for engaging someone I thought was reliable.