Pi 5 won't turn on and blink 3 long green light blinks and 3 short

I am having some problem with my newly purchased raspberry pi 5, it’s blinking 3 long green light and 3 sort, I have tried everything and unable to fix it. Is it a hardware issue ? I got both official active cooler and 27W power adapter.

Anything connected to the GPIO header? What do you see if you remove your SD Card and Boot up? What is your boot media and how did you create it?
Have a look at this.
Configuration - Raspberry Pi Documentation

I tried everything, currently there is nothing attached, only raspberry pi and it official adapter. I created the boot device from official pi imager.

If I remove everything including SD card and then give power in that case also same thing happened.

Sounds like a hardware issue to me? Might be time to contact tech support directly.
Contact Us for Raspberry Pi Technical Support - Pimoroni

I am sorry but I have not purchased it from Pimoroni, I just posted my question expecting some resolution. I am from India and I got the pi from amazon, and looks like the seller was a scam

I found two pertinent questions on Stack Overflow on this topic. One involves a recently-bought Pi from an Amazon seller where the unit did originally work but then failed overnight. Another also involves a sudden failure. The latter question links to a post on the Pi forums which suggests that the PMIC (power management IC/chip) was problematic on early Pi4 models.

The PMIC also emerges in a topic on the Pi forums where a similar situation has arisen, again with a previously working board, albeit a CM4. The PMIC and GPIO expander used in the Pi are apparently “critical to booting”. Another topic covers the issue on the Pi 5, with the initiator mentioning the debug probe to get some kind of diagnostic information, and an Amazon seller is also mentioned.

Indications are that if the PMIC has failed then there is no easy fix, unfortunately. It seems that people in this situation have tried firmware upgrades without success, but maybe the debug output via the UART can be helpful and a firmware upgrade might work for you.

Disclaimer: all of this is based on what I discovered by searching around. I don’t have any personal experience with these products.

The Pi imager utility has an option to create a firmware flash SD Card. Can’t hurt to try it, but don’t hold your breath. If the Pi can’t boot at all it won’t work.
Select Raspberry Pi 5 for the device. Then under the operating system option select Misc utility images. Choose “SD card boot” (this will install the default EEPROM firmware)

Thanks a lot, these are the exact issues I am facing.

Already have done this, this way I am getting the green display. But if I try to boot or power my pi without boot loader, then again IC2 error is coming.

I do believe your Pi has a non recoverable boot error. IMHO, replacement is the only option.