Boot-looping devices can often be tricky to put into preboot but you've handled that ok. An otherwise-healthy device will normally not drop preboot nor lose the USB connection once the flash is initiated. Because your 1490 has spontaneously developed a boot-loop after storage, it may be a physical hardware failure rather than a bad on-board file or a firmware corruption causing the problem... although usually an unreadable fw region throws a "System Software Missing" screen message rather than causing a boot-loop. The message from Updater about being "unable to program the requested memory region" unfortunately is very often an indication of the flash chip beginning to fail. The memory is made up of various discrete 'regions', as mentioned, some of which contain the firmware/system software required to properly boot and operate the device. It may be that one of those, rgn14 being the most likely, is fatally affected and can no longer accept a flash due to damage affecting it. Flash chip failure is often progressive and always eventually it's total, resulting in a dead device which no longer even powers on.

There can be other less likely causes of that error, for example, a dodgy USB cable or a loose USB socket that's 'making & breaking'. Less likely is using USB3 rather than a USB2 port, using a front port or via a hub rather than a rear port on a desktop. Therefore, to eliminate any of those faint possibilities, use only a 'known-good' cable and a USB2 port which connects directly to the computer's motherboard to flash fw. Check carefully that the device's USB socket has no movement, it it's wobbly the solder connections to the board might be cracked.

Cure fw is only of use to stall the boot process and re-enable Mass Storage Mode so that a bad file can be removed or a reformat to be done in an extreme case of file system corruption. It really cannot help in recovering a device with a firmware problem, that needs a different approach. Cure fw in that case will just turn a boot-loop into a stalled boot and then still require original fw flashed. Nor can cure fw do anything for an impending flash failure of course. If it is only a 'soft' corruption of data in a firmware region then flashing with original fw from Updater will be successful.

After eliminating all cable/port as possible connection failures, I'd be holding onto the hope that this is a soft-fail rather than the flash chip dying and just keep trying to flash it, over and over, as i've suggested above. As a last resort you could try opening the case and disconnecting the battery for some hours to completely drain the PCB. That will occasionally restore a stubbornly boot-looping device albeit rarely.