Computer won't power on

Hi guys. Looking for a little help identifying this problem. My computer will not power on. Upon pressing the power button lights and fans spin for half a second before shutting off. With a little bit of trouble shooting we organised a replacement PSU. Following removal of the current PSU I tested it in an old computer and it works fine. Totally stumped by this and can only really assume it would be the motherboard at this point. But really unsure as to why that would fail like that. The computer sees moderate use but it well looked after. Has seen no water damage. Is not dusty or hot. Have had zero problems since initial set up. And the computer has only been moved twice for cleaning. I will post the specifications below when I can work it out :p. It is a pc specialist pc. Was also wondering if anyone had any idea of what a repair time might be. Escape From Tarkov has just wiped and I feel utterly lost without my squad lol! Thanks a lot. Sam. Specs to follow.
 
Case
COOLERMASTER MASTERCASE MC500M GAMING CASE
Processor (CPU)
Intel® Core™ i9 10 Core Processor i9-9820X (3.3GHz) 16.5MB Cache
Motherboard
ASUS® ROG STRIX X299-E GAMING: ATX, USB 3.1, SATA 6 GB/s, Wi-Fi AC - RGB Ready
Memory (RAM)
32GB Corsair VENGEANCE DDR4 3600MHz (4 x 8GB)
Graphics Card
11GB ASUS ROG STRIX GEFORCE RTX 2080 Ti - HDMI, DP
1st Storage Drive
2TB SEAGATE BARRACUDA 2.5" SSD, (up to 560MB/sR | 540MB/sW)
2nd Storage Drive
14TB SEAGATE BARRACUDA PRO 3.5", 7200 RPM 256MB CACHE
1st M.2 SSD Drive
32GB Hard Drive Onboard (eMMC)
DVD/BLU-RAY Drive
16x BLU-RAY WRITER DRIVE, 16x DVD ±R/±RW & SOFTWARE
Power Supply
CORSAIR 750W RMx SERIES™ MODULAR 80 PLUS® GOLD, ULTRA QUIET
Power Cable
1 x 1 Metre UK Power Cable (Kettle Lead)
Processor Cooling
Noctua NH-U14S Ultra Quiet Performance CPU Cooler
Thermal Paste
COOLER MASTER MASTERGEL MAKER THERMAL COMPOUND
Sound Card
ONBOARD 8 CHANNEL (7.1) HIGH DEF AUDIO (AS STANDARD)
Wireless/Wired Networking
10/100/1000 GIGABIT LAN PORT (Wi-Fi NOT INCLUDED)
USB/Thunderbolt Options
MIN. 2 x USB 3.0 & 6 x USB 2.0 PORTS @ BACK PANEL + MIN. 2 FRONT PORTS
Operating System
Windows 10 Professional 64 Bit - inc. Single Licence [MUP-00003]
Operating System Language
United Kingdom - English Language
Windows Recovery Media
Windows 10 Multi-Language Recovery Image - Unlimited Downloads from Online Account
 
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