You can suspend the 5 year rule for up to 10 years while you are on qualified extended duty. Your suspension period ended when you retired in 2015. If you sold before 2018, you could have used the 5 year rule to exclude part of your gain (counting 2 years before active duty that you lived in the home, and the 3 years after, as your 5 years, and ignoring the period of suspension).
You waited too long, and you no longer qualify for any capital gains exclusion.
