Welcome to the forum, ballparq1.
My error light flashes 15 times
Yes, an ink cartridge is not recognized. Curious that the lights are still on for all cartridges.
Did this error occur after you replaced a cartridge? If so, then replace that cartridge with a new or known working one, preferably OEM to decrease the confusion that another aftermarket cartridge from the same seller might have an issue from that batch.
If that resolves your issue then ask the seller of the nonfunctional cartridge to refund or replace the nonfunctional cartridge.
Seems like I got a message when printing the other day that my ink overflow tank was nearly full or something to than affect. I dismissed it at the time.
When the ink absorber counter finally reaches FULL then the printer will no longer print.
I don't know if it is possible with your printer, but, if you could reset the ink absorber counter using a Service Tool then you could continue to print. If you wash and dry the ink absorber after dismantling the printer, or replace with new bought somewhere (?). Otherwise, eventually ink will overflow the absorber and leak out. It is advised to set the printer on a tray for when this might happen to catch and contain overflow ink so as to not stain your furnishings and floor.
Another school of thought, and maybe your only choice if you cannot reset the ink absorber counter, is to buy a new printer.