LED lamp turns off when turned on

This is probably the LED driver inside of your flood lamp enclosure discharging any charge that is left in its circuitry. I couldn't imagine this being in issue, especially is its a very short flash

It sounds like the when the lamp does not use a hard mechanical brightness switch. Responding to the brightness control is done in software. When power connection is severed, it is not able to remember its previous brightness setting, and returns to a default of "off" when power returns. You can test that by plugging it into a regular outlet, unplugging it while on, and replugging after 5 minutes.

This type of lamp is not suitable for use with a hardwired light switch or smart controller which interrupts power. Since the product doesn't clearly state that up front, you should have no compunction about returning it.

I just saw a lamp at IKEA with a similar problem. I did the "unplug" test and it did not relight on replug. It had a "power brick" with a lightweight DC cable to the lamp. See also the PC board plainly labeled where white is switch and the two active conductors red/black is Vin+ and GND-, the +-, colors, and "GND as conductor" are all hallmarks of low voltage DC power, along with the wall-wart. DC isn't bad, safer actually, but it invites more "complicated" lighting controls which may not behave as expected.