Model dc618. Why is light flashing constantly and it will not fire?

https://www.weeklytools.com/how-to-use-a-nail-gun-with-an-air-compressor/

We may not need a drill machine almost the whole time. But there is a demand for a pilot hole during the home finishing process. This post is not for you if you are a professional. However, in most of the cases, we observe the necessity for a pilot hole. From wooden doors and windows ...

lube ram and inspect for damage -check and inspect trigger

Continuous flashing indicates low battery charge or poor battery connection. If lights flash 4 or 5 times indicates possible control module fault.

Need a little more info not sure I can help what is model and brand
propane natural gas
First have you tried a mfg website ,second put brand and model number in a search engine see if anything comes up
Last I would venture it is the thermo couple is either bad ,dirty, or has slipped and not staying hot
Take a brillo pad (new and not wet) locate the thermocouple and gently sand it off and try it again
Look for an owners manual on line and see if you can find that to see what the 8 flashes are

firstly its always better to change both of the bands even if one is broken this always keeps the drive trim.all seems well clean all the contacts ie battery and gun (do not use any cleaning products this will cause grease)just wipe clean with paper towel.

The link below is where you can download the owners manual. The link is on that page near the top right hand side under the area marked downloads. Page 5 will show you were the switch is located that switches the tool from sequential fire to bump fire.

DeWalt DC618 parts and operations manuals

Yes, if it is not pushing the safety back far enough. Also check for pieces of nails debris in the slave slide.

Check the battey then take it out and check the driving rod. On the front of the gun, flip the latch and make sure it is pushed all the way back.
make sure you have nail, of course. put the battery back in. If al that does not work, have it services at a dewalt service center.

I have both the DC616 and 618 and have used them sucessfully for about three years. Two main things go wrong. There is a drive belt that breaks (drives the spool that give the energy to drive in the nails), second are two small rubber bands on either side of the drive head that break. The bands can be accessed by taking off the front silver cover, the drive belt is access by spliting the case. Make sure you are using the correct nails or the drive pin may become bent and will jamb repeatedly. Hope that helps!