Board isnot powering up

Hello Group,
Good day. Please bear with me, as I’m a newbie to Beagle Bone Black. Just got the board(Rev-A5A) a few days back. Right since then, I’ve been experiencing this issue of the board not powering up using the DC power adapter(5V/1A) that I purchased along with it. Upon connecting the power supply & pressing the Power button as indicated in the manual, the blue led(D1 as per schematics) blinks faintly & nothing happens. I have checked the power supply output of the adapter and that shows 5V DC.
However, interestingly, upon connecting the USB cable the board powers ON(blue led D1 glows, followed by the other 4 leds D2-D5) and was booting up properly, up until now. Presently, I observe that the board is not booting any more even when powered via USB : The Led D1 lights up in full brightness & stays as such. No further activity is seen on the board nor any messages appear on the serial console. There is no change in the original behavior scenario either - i.e., powering up via the power supply has the same state as explained. Please help.
Thanks in advance.

P.S : I’m posting this as a new one as I’m unable to relate this issue exactly with similar matching posts.