Hi @alexa9672,
I think that your TV has a chassis model number of [https://elektrotanya.com/sony_kd-65x8000c_chassis_gn1t_sm.pdf/download.html#dl|GN1T] but not 100% sure of this.
Check if you can find this or a similar number on a sticker somewhere on the inside of the back cover or somewhere on the chassis of the TV. If a different number search online for ''(insert chassis number) service manual'' to hopefully find one.
If it is the correct number then unfortunately a 4 blink error code (see p.8) doesn't indicate what the problem is. Also the blink error codes only pertain to when the TV is first started and not when the TV has already turned on OK even for a short time and then fails.
Did you try a power refresh at all, just in case it is a software problem? Disconnect the power to the TV and then press and hold the TV's Power on button for 30 seconds and then release it. Reconnect the power to the TV, turn it on and check.
Just verifying that there's been no damage to the screen at all e.g. small crack etc? With some other Sony TVs a 4 blink code can sometimes mean a faulty screen. Just checking.