1) Be sure that the image was correctly made with the official how-to.
If by chance you were using this
gunzip -c audiolinux_203.img.gz | dd of=/dev/sda1
instead of
gunzip -c audiolinux_203.img.gz | dd of=/dev/sda
a partition will be missing

2) Disable SecureBoot, FastBoot and other Windows options

3) Disable completely all Intel securities options, if you have Intel bios

4) Disable legacy boot, so that you have only UEFI (this is important for Intel NUC)

5) Set the default boot to the USB or the internal HD where you installed audiolinux

6) Disable all other boot options (including network boot), excluding the one you are using

7) Remove all other hard disk and USB drives connected to the computer

8) Try to change USB port (this happens a lot of times, some USB ports are not boot compatible)

9) Check if your USB stick is supporting booting. Some does not. SanDisk Extreme is the one recommended

10) Eventually press F10 or F11 or some other key (see bios documentation) to open the boot menu. If you don't see nothing, most probably the audiolinux copy is corrupted or incorrectly made

11) Poweroff completely the computer, detach the power chord, wait some time and poweron. Uefi will refresh devices.