Buy Now buttons not working on Jumia's Nigeria Black Friday website

I've been trying to buy a couple of things from Jumia Nigeria's shopping website during the Black Friday deals and I've noticed that some of their Buy Now buttons are not working and this is for items whose time limit is yet to expire.

For instance, I tried buying Jumia's Double Awoof N5000 voucher for N2500 and after clicking the Buy Now button, it wasn't working but when I tried buying the N2000 voucher for N1000, the button worked. The sale for the N5000 Awoof voucher I was trying to buy has not yet expired since it had 3 hrs remaining on it and there were no remarks or notes saying that the deal has been totally sold off.

I also tried buying a Samsung HDTV discounted by 40% but that still did not work after I had clicked the Buy Now button several times. It seems that Jumia might have intentionally disabled some Buy Now buttons for items they sell on their store once the items reach a particular number of sales for one reason or another.

I have included a video to show the problem I experience while trying to buy a voucher from their store during the Black Friday sales. I think it would have been better not to even list the product or replace the buy now button with a notice that sales sold out rather than wasting people's time who might want to buy the deal within the time limit.