Translation:I usually go cycling alone on weekends.
In my experience, Duo has trouble understanding that "on the weekend" and "on weekends" can be synonymous, e.g. in a sentence such as this one, where the verb is in the simple present, especially when there's an adverb such as "usually".
While this could be a function of the newness of the Chinese course, the French course has suffered from the same problem for as long as I've been on Duolingo (2.5 years at the time of this comment).
I often ride my bike by my self on the weekend.
said correct answer was same except: myself, and weekends
"Usually" would be better translated as 平常 whereas 经常 is more closely synonymous with 常常 meaning "often" or "frequently" https://resources.allsetlearning.com/chinese/grammar/Comparing_%22changchang%22_and_%22jingchang%22
They're similar, although I'd probably translate them as normally and keep 经常 as usually.
Instead of posting all this here in the comments, just suggest these answers at the correct spot!
I think they use "at the weekend" instead of "on the weekend" in British English.
It corrected me to say "at weekends I usually go cycling by myself." There is no report button for the English sentence being unnatural or wrong, so I'm reporting it here.
I usually ride my bicycle alone on the weekends. This was rejected. And do you want to know what the answer was supposed to be according to Duolingo? "I usually ride my BIKE alone on the weekends" Really? really? I get called out for spelling out bicycle????
"On the weekends, I often ride a bicycle alone." should be accepted. Duolingo wants "my bike" in lieu of "a bicycle".
Similarly, for "On the weekends, I usually ride my bicycle alone." Duolingo wants "bike" in lieu of "bicycle".