Why isn't the sale price displaying correctly in different currencies?

[TubieLove]

Hi, I'm having a sale on some items and have set the pricing correctly at the 'compare at price' and 'price' sections.  Sale price is showing correctly on my website in my selected currency, NZD, but a customer in Singapore is not seeing the sale prices on some products when she views my website in SGD.

Screenshot showing NZD

 

Screenshot showing SGD

Row of tube pads is not showing sale price but row of items above is.

I have the basic plan and my theme is Impulse 4.1.4

Thanks, Tammy