"I did not meet them at home."
Translation:Jeg traff dem ikke hjemme.
"Jeg traff dem ikke heime" is an accepted translation, so if you're sure that you didn't have any typos it sounds like the app was acting up. Fingers crossed it was a one time thing.
'Ei' is a variant of 'ikke', so that would be correct.
'De' should be 'dem' regardless, as it's the object in this sentence.
I hope that clears everything up. :)