"Please turn off the TV."
Translation:Выключи телевизор, пожалуйста.
It could work if you replace imperative with infinitive, so that it becomes «Про́сьба вы́ключить телеви́зор» '[There is a] request to turn off [the] TV'. We actually use it instead of «Пожа́луйста, вы́ключите телеви́зор» 'Please turn off [the] TV' sometimes, but «Пожа́луйста, вы́ключите телеви́зор» is a much more common version.
I'm not sure if Duolingo accepts «Про́сьба вы́ключить телеви́зор», because it's less used often.
It should be accepted too (выключи is less polite and used with friends, выключите is used with people you don't know well). If it's not accepted, please use the Report button.
If you type exactly what it asks for, it's wrong. You have to INCLUDE the comma (necessary) AND DELETE the space between the comma and the last word, which is patently wrong. In other words, you have to write incorrectly to get credit. I tried several times before I realized this