NZ Off topic

I can't help with the spray, but if that's a mulched area - my go to for killing anything underneath is to put down some plain cardboard on top then drop a good layer of mulch or compost on it. The cardboard will break down with time. I usually do this to kill off grass for new planting areas.

Edit: I looked up the Yates Moss and Algae product and it's just Benzalkonium Chloride which is the same as the green 30 Seconds stuff. You could try a product with a different active ingredient. Like this Kiwicare product: https://www.kiwicare.co.nz/product/lawnpro-mossclear/. Or try with a higher concentration in your sprayer.

Why would you want to get rid of it?

I have no idea how you might get rid of it, but it likely grows there because the conditions allow it to thrive. If you kill it, it will probably just come back.

Do you have options in changing the condition? Is it wet and shady, which could be helped by trimming back a tree, or something like that?

Also, roundup/glyphosate can be difficult to get to stick to "slippery" leaves. You can usually add some dishwashing liquid to it to help with that, but soap/surfactants are really bad for insects so try to keep it away from flowers.