also I tried on Alpha Sapphire 1.4 with 3 versions of BootNTR - not mode 3 -, 3.2, 3.3 & 3.5 and here the PSS says "error, try later"
Is your firmware updated? Is Luma updated? At this point you need to switch over to B9S, this will help.
https://3ds.guide/updating-to-boot9strap
There's something wrong on your end, because Michi's updated version works perfectly fine.