Epson STYLUS PRO 9000 User Manual page 108

Note:
There is a protection system against improper cartridge insertion.
If you cannot insert the ink cartridge smoothly, the type of cartridge
may be incorrect. Check the package and production code.
8. Push the cartridge clamp backwards. Make sure the
corresponding Ink Out light goes off.
Note:
If the Ink Out light remains on, the ink cartridge may not be installed
correctly. Remove the ink cartridge and then reinsert it as described
above.
108
Maintenance and Transportation