Turns out there was nothing wrong with my existing ink cartridge, it was just my printer having a moment.
I could only buy new inks in packs of four, so I now have 3 unopened Light Magenta (ie pink) ink cartridges going begging. There's no way I'll get through them before expiry date.
They are H-363 XLLM, brand is PerfectPrint, and they are compatible with HP Photosmart 3108 3110 3210 3310 8200 8230 8250 8253 C5140 C5150 C5180 C5183 C5188 C6150 C6180 C6183 C6188 C6200 C6250 C6280 C6283 C6288 C7180 C7183 C7200 C7250 C7280 C7283 C7288 C8180 C8183 D6160 D7160 D7163 D7260 D7263 D7360 D7363 D7460 D7463 P3210