What about "did not work"?
Based on other exercises, that should be correct.
Perhaps even "was not working", although Duo is inconsistent about that form of the verb.
It is now accepted 15.100.2019
"Ivan was not working in this country." is not accepted as of 2020-07-01.
Wait, it might be. My autocorrect typed "on this country" which is clearly wrong.
странЕ, not стрАне
Well, they say странЕ.