1.The paper roll is not installed properly, causing the printer cover to not be closed in place

When red light of the printer is always on,it shows that the paper roll is not installed properly, causing the printer box cover to not be closed in suitable position. So please reinstall it correctly and put the box cover properly.

2.Printer is out of paper

When red light of the printer is always on,it shows that the printer is out of the paper.So please check whether the paper roll can be used up,and  just pull out the paper outlet.

3.High temperature of print head

When red light of the printer is always on,it shows that the print head is in a high temperature, so please check whether the print content and the number of sheets are too high, causing the high temperature, and just  let the print head cool down naturally for three minutes and it will be okay.