I am 68 and self employed, divorced from Spouse #1(currently age 26) for 26 years after a 12 year marriage. I am continuing to earn. I went to SS to file on my ex spouse' record a restricted application while my credits continue to grow until age 70. I was told I could not file because I had already filed on my children's behalf when I reached FRA and they were both still in school.Now that the youngest is off to college and I am no longer collecting,why cannot I file the restricted application on my ex' record?

Mark,
Once you file for retirement benefits you can only "un-do" that filing by withdrawing your application within 12 months and paying back any benefits that you or your family members have received. Since you didn't do that you are still entitled to retirement benefits, even if you aren't actually receiving any benefits due to the Earnings Test. Filing a restricted application for spouse's benefits only means that you would be entitled to only spouse's benefits. Since you are entitled to retirement benefits you can't simultaneously be entitled to only spouse's benefits.
Best,
Mike