Our printer is stuck in copy mode and is printing

It may be specific to your OKI printer driver. Refer to it's manual.

The MB451W uses electrostatic toner and does not have print heads. Follow the cleaning instructions beginning on page 172 of your User's Manual. If you don't have it handy, you can download it from the OKI website. (The link is for the English language manual.) http://my.okidata.com/mandown.nsf/196efed9e03ff0d1852576ee00476710/3854f93fb3d0181185257a7f004eddcb/$FILE/MB461_MB471_MB471w_MB491_ES4161%20MFP_ES4191%20MFP_MPS4200mb_Basic_UM_E.pdf.pdf

Note: on page 174, the manual recommends "soft tissue paper" for wiping off the LED array lens. Lens-cleaning paper or cloth for plastic lenses should work and is less likely to leave lint behind.

If you are getting random black blobs on the back of your printout after cleaning the printer as recommended, the fuser is dirty. If the fuser cleaning strip is accessible (a felt strip that wipes off the fuser roller during operation), gently scrape it clean with a knife blade held perpendicular to the strip, then clean the debris out of the printer. (CAUTION: the printer must be off long enough to be cold before working on the fuser!) If you can't get into the fuser, use the following procedure: Get matte-finish paper of the thickest stock your printer will handle. Put several sheets of this paper in the paper tray. At the computer, type a single space on a blank document, with no headers or footers, then print the blank page (trying to print with nothing at all usually doesn't work). This should pick up some of the trash. If you still have problems, open a graphics program and draw a solid black rectangle all the way across the page ("portrait mode") and about 4" high. Place a copy of this rectangle 2" below the first one. Insert a page break, and put a white object (anything white or transparent, with a white boundary) on the second page. Print double-sided. The black rectangles will pick up dirt from the fuser roller and the heat will make it stick to the paper toner. Repeat if necessary, then remove any unused cleaning paper from the tray.

I would suspect that the you didn't get the drum back in properly. There are contacts on the drum casing that need to make contact with the base of the printer. It's possible that either it's not seated properly or that some toner is lodged over the contact preventing a good electrical connection. Try removing the drum again and carefully reinsert.

we have OKI microline 280 elite , 9 pin printer, it's print blank why
?

I still love you

There are two main caused of blank printouts in inkjet printers:
Low ink level
Clogged nozzle of the ink cartridge
Refer to this article:
Blank Page while printing

Snap off the cover off around it and attempt to release the button. Only shot.

you looking at 3 posibles one is the scanner may need to be replace or the low voltage power supply or you looking at a posible drum problem

Either the light source is failing or you have a piece of paper stuck in the way of the LED's and the drum.  Check the paper path very carfully to make sure there is no dirt or debris in the paper path.

check your rribbon.
also cjeck your head.
try to tast page from printer properties.
also try to print from dos .
check your printer datga cable.change it