As they say, you learn something new each day.
Epson ink jet had a severe head clog cleaning wouldn't fix. And the ink had nearly run out too, and no spares left.
Ordered up a cleaning kit and some new non original carts from Ebay. A fraction of the cost of maker's ones. Had used several before. The machine nagged about them not being makers ones. but worked well enough.
Set it to the cart changing position, and removed it to the workbench. Cleaned the heads using the cleaning kit, and installed a new set of carts.
On powering up, got carts not recognised and it would do nothing.
And of course I assumed the carts were faulty.
But then decided to Google.
Seems the software hadn't reset due to them being changed while powered down.
Cure was to remove them while powered up. Wrap in clingfilm. Power down and leave a few minutes. Power up, and refit.
Now recognised as non OEM, and working again.
And machine working well after a couple of cleaning cycles.