Hisense tv fault

There are 3, possibly 4 boards in most TVs. If your are up for it and are aware of the danger & risk of electric shock/electrocution then you could swap out the boards. Most boards can be had for around £30.
If the red light flashes two, three, or five times, it indicates an issue with the power board, the inverter, the mainboard, or the backlight. If the light flashes four or 10 times, the issue could be with the inverter board wires or main logic board. Sadly it's not easy to narrow down the fault better than that without further diagnostics.
So by swapping out the parts - if you are lucky (and assuming the screen isn't damaged) - you could have it up and running for £30 and a little effort (as long as you are aware of the risks and can use a screwdriver). It's unlikely to be the t-conn board or multiple parts. Most of those faults can be fixed with components that cost less than a penny in bulk, the trick is having the skill, tools & time to do a component level repair.
Sadly the consensus is that a 3 year old, £250 TV just isn't worth the effort to fix!

For what you paid for the tv I'd say it's not going to be worth repairing and just buying a new tv

Do you have a warranty from the seller? If so, then let them sort it

Usual dull response:
straightforward Consumer Rights Act claim against the joker trader that sold you the prematurely busted rubbish. No warranty required.

Standard example CRA ramble to present to the trader (and credit provider if all/part payment was paid directly to the trader via credit):
which.co.uk/con…lgZ

Example of successful CRA claim for TV that prematurely busted in year 4 of ownership:
hotukdeals.com/com…479