"No podemos encontrar su número de teléfono" should also be accepted. Reported June 2018.
That sounds awkward, a native speaker would not use poder in that sentence.
9/20/18 "su" is still not accepted.
Still not accepted 21/11/18
"Su" accepted 3/8/19
When I lived in South America I used the formal when speaking with an older person or to be polite.. The "tu" was used only with younger people or someone you knew well.
Where is' Can't'
The "no encontramos" (we don't find) also maps to "we cannot find" in Spanish.
"No podemos encontrar su numero de telefono" still being marked wrong on 09/27/2018. Reported
I used 'hallar' and was shot down. Any particular reason for this?
Hallar at me when you get an answer to this
This is the correct answer because the other two options are wrong. However, it is an incorrect translation.
Elizadduex's answer was not one of the options when I did this lesson. (1/5/19). Perhaps DL made a change (?).