Black cartridges now useless.

However, I did look at the prices for the cartridges and they are expensive especially the black cartridge

This printer comes with automatic ink replenishment (and if you ask for that feature, the cartridges are much less expensive than buying them via Amazon retail OR going to your friendly local office supplies store).

had I not used cheap ink cartridges.

Unless you want a constant headache and expense of being stuck buying manufacturer's cartridges, DO NOT buy any Brother printer

The manufacturer recommends shaking the black ink cartridge before installing, so I’m wondering if they perhaps skipped this step

Brother has recently introduced a compelling alternate solution: Printers with replaceable, high-capacity cartridges (awkwardly dubbed INKvestment cartridges)

Also enjoy being able to print directly from smartphones (on the same LAN) and get output that looks as good as from a PC.