Onkyo TX-SR373 AV will not power up

I absolutely love my Onkyo TX-SR373 AV tuner for so many reasons and recommend it to anyone and everyone.
I have owned many home stereo, tuners and amps through out my life. Many of which would fail to turn on at some point in time or just not produce sound without something needing to be replaced.
Most of the time if not ALL of the time if powering up was an issue it was always a fuse. Replace said fuse and abra cadabra! Like magic music is prevailing in my ears and I am happy and I am complete once again.
Well my beloved Onkyo is not the type to be so simple it seems... I attempted turning her on and like most females in my life, I have so much to learn. I thought the basic fuse change was all she needed, but nope she is more sophisticated and clearly requires more attention.
Nothing looks or smells burned on any of the boards. There are no tell tale signs of any visible troubleshooting issues. How can I come up with a diagnosis and not mess anything up?
And does anyone know of any possible common issues or factors with this particular model or manufacturer.
Thank you for reading this far and I really appreciate your time and any help...