Epson EPL-N7000 Reference Manual page 353

Can't Print Duplex
The printer has encountered problems during duplex printing.
Make sure you are using an appropriate type and size of paper
for the Duplex Unit. The problem could also be a result of
incorrect settings for the paper source that you are using. Pressing
the N Start/Stop button will print the rest of the print job on only
one side of the paper. Press the + Cancel Job button to cancel the
print job.
Cart Near Empty
The printer is running out of toner. It is recommended that you
replace the imaging cartridge. See "Replacing the Imaging
Cartridge" on page 257 for instructions.
Check Paper Size
The paper size setting is different from the size of paper loaded
in the printer. Check to see if the correct size paper is loaded in
the specified paper source.
To clear this error, select Clear Warning from the control panel's
Reset menu. See "Reset Menu" on page 410 for instructions.
Check Paper Type
The media loaded in the printer does not match the paper type
setting in the printer driver. Media that matches only the paper
size setting will be used for printing.
To clear this error, select Clear Warning from the control panel's
Reset menu. See "Reset Menu" on page 410 for instructions.
Collate Disabled
Printing by specifying the number of copies is no longer possible
due to a lack of memory (RAM) or free disk space on the optional
Hard Disk Drive. If this error occurs, print only one copy at a time.
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Troubleshooting