My last name is to long, what do I do?

 You can fix that by removing the last letters that don't fit.  The IRS matches the social security number with only the first few letters of the last name.

I`ve tried several times and it doesnt work :(

Just enter the first 20 characters and be certain that your Social Security number is correct on your tax return

Same thing for me. I end up filling by mail because it fails every time.

The total characters allowed are limited for the entire name ... so reducing your first name to an initial and deleting the middle name usually works.  I do believe the total allowed is 35.