Swapped out my 8 year old OCZ 1000w Gold with a new Seasonic 850w Prime Titanium. MOBO lights come on But does not power on. Checked all cables they are seated correctly. MOBO uses and 24pin and a 8 pin for main power Checked connectors from power button and reseated them. Still nothing. Plugged in my old power supply and its working like normal. Anything else i could try? Thanks.
I gather you tried to turn the system on with new PSU with the case power button connector connected, right?
Something might not sound quite logical (since old PSU works) but might just work and will rule out the button connections shorting or anything.
After you connect the Seasonic's 24 and 8 pin connectors to the motherboard, and throw the PSU's own switch on, try turning it on/booting instead by shorting the 2-pin PWRSW pins on the f-panel by touching them gently with s screwdriver or something metal.
You can check to make sure where and which two the pins are in the motherboard's manual.
You're not using the old OCZ cables, are you? You didn't specify which OCZ PSU you had and sometimes going from modular PSU to modular PSU, we see people trying to just plug in the old cables connected into their components into the new PSU.