The Australian stocks stopped working for me around a week ago. It was fine before then but now I am getting errors that:
'This ticker is not available’
for every ticker.

the range is too big to be returned in one request
try a smaller range https://yahoo-finance127.p.rapidapi.com/historic/pme.ax/1m/7d

I have similar issue with historic data endpoint.

Example: https://yahoo-finance127.p.rapidapi.com/historic/pme.ax/1m/3mo

Response: {“message”:“Either PME.AX is not a valid ticker OR historic data is not available for this ticker”}

I cannot recreate the error you are describing ,
I think it may have been a glitch.
Is this error still occurring?