A very common way to spell T.V. in Swedish is teve. That should definitely be a correct alternative answer!
Did you get this as a 'type what you hear' task? There's a problem with making the machinery accept spelling variants in these. We can't fix that right now, but I'll turn that excercise off for this sentence. On the 'translate into Swedish' side, teve is an accepted answer.
Yes, there is "television", but only in a strictly technical sense (or really old-fashioned, 1950s when it was new to Sweden).
C'mon folks. I got this wrong because I wrote tv and was informed that the correct answer is telly.
Then you had some other error as well and didn't realise, in which case Duolingo isn't smart enough to show you a closer solution to what you wrote.
I have just had this problem and reported it. I wrote "I watch the TV" and was corrected to 'I watch telly'. As far as I am concerned there is no difference.