Translation:These are the men who stayed at the hotel yesterday.
In addition to the reply by G.Georgopoutos which addresses the use of the past I'd like to point out that we do not use Past Continuous with stative verbs. That is verbs showing conditions "see, love etc" unless they are used in idiomatic phrases. For more information on this see here:
My answer, pasted below, was rejected, and in Duolingo's correct Greek translation, the word χθες was underlined, indicating I believe that my alternative spelling, χτες, was wrong. My sentence: Αυτοι ειναι οι αντρες οι οποιοι εμειναν στο ξενοδοχειο χτες. (I omit accents because on my current keyboard using them causes me to make a lot of mistakes.) Was χτες the reason my answer was rejected?
Please note this reply was written before your comment about the Listening Exercise. Thanks for the feedback.
These are the alternatives we accept for "yesterday"
So, no χτες was not the reason your answer was rejected. nor were the missing accents. That means you had a mistake. What you show in your comment looks correct except for the total lack of accents or there was another reason for it's being rejected.
*TIPS TO MAKE LEARNING EASIER + HOW TO REPORT A PROBLEM
And check out the Greek Forum here with more links.
If you have any questions just ask.
"Was this a listening exercise?" since that would be the only reason to underline "χτες"