what's the problem
I see what the problem is.
Том объяснил мне, в чём проблема.
Tom explained to me what the problem was.
Я до сих пор не понимаю, в чём проблема.
I still don’t understand what the problem is.
Want to know what the problem is?
So, what’s the problem?
Он не мог понять, в чём проблема.
He couldn't understand what the problem was.
Я точно не знал, в чём проблема.
I wasn't exactly sure what the problem was.
Do you understand what the problem is?