Added CNAME record, but still doesn't work
Снимок экрана 2019-04-15 в 14.02.35.png

I can not add a site, this window appears.
Снимок экрана 2019-04-15 в 14.03.52.png

What am I doing wrong?

The question is removed, it all worked!

DNS propagation takes time so after any change, you need to wait a few minutes. Worst case, it can take even up to 48h.