I've got several RB962, and each time I need to netinstall one there was some kind of problem - it won't netinstall like other MT devices.
If I remember correctly, the last time problem was solved with failsafe format (supply power while keeping reset pressed, hold reset for 300+ seconds), then it netinstalled correctly.

Today I've ran into RB962UiGS-5HacT2HnT that won't netinstall.
Resetting its config caused the router to bootloop. (I'm not sure if protected routerboot was enabled, but most probably no.)

I've kept the reset for 300s (PWR, SFP, and Eth1 LEDs on) as I've done before, and power cycled the router.
It still fails to netinstall (and I've got a shorter bootloop if power is supplied without keeping reset pressed)

I've repeated holding reset for 300s (PWR and Eth1 LEDs on, SFP flashing), and power cycled the router.
Now when I supply power (with or without reset pressed, PoE or adapter) the only LED that comes up is PWR. No link on any Ethernet port.
Looks like I've finally bricked it

Is there any way to recover the device?

We had several problems with hap ac lites (RB952Ui-5ac2nD) and some of them bootlooping after software upgrades. We normally do have protected-routerboot activated to avoid erased devices when customers really like to press reset buttons.

We have learned a few things from this, since hap ac lite and hap ac are both MIPSBE devices but not using the same chip im not sure if my tips will apply in your case (you will most likely know many of these points but just to make sure everything is correct i will include even the "totally clear" steps):

-> Always make sure netinstall is running on a computer with dedicated lan-port (usb-adapters are totally unreliable)
-> Turn all other network adapters off (if you have any)
-> Set ip-address and gateway (even if there is none) on the windows computer
-> Dont power cycle the device after pressing the reset-button for 300 seconds - just wait. It takes ages but it normally comes back after a few minutes. Correct way would be: Plug the power out, press and hold reset, plug power in, wait ~310 seconds, release the button, wait a few minutes.
-> Try multiple netinstall versions (sometimes newer or older versions did the trick, can not tell why)
-> Try another computer

Hope that helps

My old 0.02$ to this topic: viewtopic.php?f=1&t=93307&p=490460#p490402

Looks like power cycling the router after 300s format had bricked it.
And this SFP LED steady on for first 300s / blinking for second 300s makes me think it erased primary bootloader first, than backup bootloader.

I always disable all other adapters and when running netinstall or similar utilities (netinstall/WinBox are really good when compared to utilities from other brands).
The adapter configured with correct IP/subnet, the network card is a problem-free PCI-Express one.
Moreover, I usually grab a known working spare MT and try to netinstall it to check if netinstall works OK in the current setup.
It worked today too. Haven't helped though.

Am I right that all the data (firmware, bootloader, config, hw config - MAC, serial, ROS key) on the device is stored in SPI flash?
It's not a problem for me to desolder this chip from working hAP ac, dump it, and flash the dump into the bricked device.
But I'll need to save hw config block (if it's not erased already).

I've finally got to this issue, desoldered SPI flash and found it to be completely empty. No boot block, no config block, nothing. Just 16Mb of 0xFF.
So I can confirm that hard resettng hAP ac twice causes complete flash erasure.

I've debricked the router by flashing a dump from another hAP ac into it, but ran into obvious problems with the same serial and MAC on two routers and a broken license.

The issue was submitted to MikroTik support, let's see if they'll be able (and willing) to help.

The support have refused to provide me a new key for unbricked device, citing it has the same serial as fullflash donor. (Thanks, Captain Obvious!)

That's haven't been unexpected, to be true.

So I have to dig deeper
I'll keep this thread updated should I get any results.