"On the platform, we found out that our train was delayed." is identical in meaning to "We found out on the platform that our train was delayed." Both are grammatically correct.
https://uloz.to/!LLxTPQdnLg8u/ Why it does not accept dozvěděly, but only dozvěděli?
There are 397 translations which are currently accepted and many of them end with -y. Unless you provide your whole sentence, I can't check it.
Is there any reason that "we found out that our train is late" is not accepted? It was corrected to delayed but it seems exactly the same to me.