After changing to custom domain and adding CNAME given by Pythonanywhere in domain registrar settings. I got this on Web tab page:
There is a problem with your domain name configuration. Take a look at the DNS setup section below for details. Be aware that DNS changes can take some time to propagate across the internet. The exact time they take will depend on your domain configuration, but it could be as long as a day.
DNS setup: How to point your domain at your website. CNAME: webapp-XXXXXX.pythonanywhere.com Your domain's current CNAME is inpower.kiev.ua. Check this help page for more information about how to set it up correctly.
Does my domain's current CNAME must be exactly www.inpower.kiev.ua?
Here at MX Toolbox I see next:
Type: CNAME Domain Name: www.inpower.kiev.ua Canonical Name: inpower.kiev.ua TTL: 10 min