Instant Ink HP Hewlett-Packard Failure to Provide Cartridges or Refund Internet

I have been on the Instant Ink program, in which I pay a monthly fee and HP sends replacement ink cartridges whenever my supplies run low, since January 2022. I had not paid close attention to tracking when I received shipments of replacement cartridges, because they do not come on a regular schedule - they are shipped as HP detects that one or both cartridges are getting low on ink. On June 12, 2025 my HP Envy 6000 Printer stopped printing and displayed "E 0" error. The black cartridge was dry. I researched my account history and discovered that the last shipment to me had been sent in January 2024. I contacted HP (through their online chat feature, which was the only way I could find to contact them). I was told that HP had been supposed to send me new cartridges when my plan had renewed, in January 2025, but that they had failed to do so. The rep supposedly triggered a new shipment (I'm still awaiting delivery of that). I called the following day and asked for a refund of the six months that I had paid for without receiving any replacement cartridges, considering that it was HP's fault I had run out of ink after using up cartridges I had paid for in the prior plan year. HP declined. How can HP keep these monthly fees when they admittedly failed to ship me the ink cartridges I was paying for?