If you OWE tax due for those years the IRS still wants you to pay. Prepare the returns by hand and mail them in.
Form 1040Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2014.pdf
Form1040EZ Instructions https://www.irs.gov/pub/irs-prior/i1040ez--2014.pdf
Form1040 Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2015.pdf
Form 1040A Instructions https://www.irs.gov/pub/irs-prior/i1040a--2015.pdf
Form 1040EZ Instructions https://www.irs.gov/pub/irs-prior/i1040ez--2015.pdf
you will have to get the forms from the IRS website and manually prepare them. while some sites offer the software for those years, this software is usually not the "current" version and can't be updated. the return those apps prepare will probably be inaccurate. you other choice is to see a pro. they usually have the software to correctly prepare those return. if you owe, be prepared for some penalties for late filing and payment. no penalties if you don't owe