what happens to high school football player who didn't sign on national signing day ?

They can still sign for a couple days after it and if still not signed and if they are a senior they can get a preferred walk on with a college team
or sign with a DII or DII or NAIA or JUCO team

National signing day is the first official day that high school players can sign... They can sign anytime now.... If they aren't offered scholarships the can still walk on and play at a college.....

National Signing Day is the first day a player can sign not the last day.

They can sign a letter of intent later. Most sign on national signing day to take part in all the hype, but they can still sign. Some will not sign with any college and instead will "walk on" to a team and try to make it that way.

Actually, college football recruits do not necessarily have to sign a Letter of Intent on the National Signing Day. The only restriction is that the Letter of Intent cannot be signed before the National Signing Day.

Most recruits choose to sign the Letter of Intent on the National Signing Day because of the exposure they get on ESPN, as well as to get the recruiting process over with.

However, there are some recruits that do not sign a Letter of Intent on the National Signing Day. These recruits can sign a Letter of Intent any time after the National Signing Day, all the way until April 30.