My MF 5700 has a red lamp blinking and notification-check paper size constantly, even when I restart it, wont print anything, paper size is ok...

Every time there is paper jam, the printer knows the job is not completed and hence tries to re-print after the paper is removed and cover is shut.

Clear the print job from computer.
Power off the printer and Clear the paper jam (if any)
I would try to use different tray. The paper pickup roller in one path may be worn out.
eg Sheet feeder or multipurpose tray.
Load paper in new tray
Set the application to use new tray

Ensure you sue the right thickness (gsm) of the paper. Quality of paper is crucial. Too thin; too thick can affect functioning.

check if the paper size not match with that sitting in printer sitting and the aplication you use

I out of paper jam & try this print so not working on printer& blinking the light,please help me..

try to set the proper size for the paper in the printer.
press [Additional Functions] button (right of the LED display)
navigate to Common Settings
use [<-] and [+>] buttons to navigate to Select Paper Type and press and press OK
Confirm that Cassette 1 i selected (or Cassette 2 if you have optional installed)
and Set the paper type
next navigate to Reg. Paper Size, press OK, confirm again the cassette (1 or 2) and using the arrow buttons, set the paper size (should be LTR if you using LTR)

Check paper size refers to the fact your documents are for say and A4 sheet of paper but your drivers properties are set to letter size. Go into the drivers printing preferences and set the paper size to the correct value. All should work fine now.

those lamps may look good but can still be bad, they build a internal resistance and there get to the point where the tv will not come on at all.

There is probably a paper jam since you shut it off as it was printing. Turn off the printer. Remove the tray and look inside. Remove any sheets of paper you see. Open the back of the printer (the pass-thru door) and remove any paper you see. Turn on the printer. If that fails, check the blink status against the manual's troubleshooting guide to locate a different solution.

Try this:
1- Pull the cartridges out, restart printer then reinstall the cartridges again
2- The blinking can mean any of these: paper out, paper jam, cover open, printing error. Please check that there is enough paper, no paper jam (sometimes even the smallest piece of paper will cause that error, then restart both (the printer and the computer)
Best of luck

Error 5700 is usually a paper "feed" jam.Check the automatic paper feed area to see if any paper is jammed

basically for this printer I have found that just restarting your computer will solve almost anything. make sure there is no paper left jammed in the printer and restart. sometimes you have to delete the print job in the printer que. there should be a printer icon down my your clock, right click, open active printers, and delete your file. restart your computer and try again