Can't log into minecraft.net using Mojang account is some circumstances

Hello! I have a Mojang account. I have a problem. Everytime I log into minecraft.net using Mojang account it gives me an error.

Steps to reproduce:

1. Go to minecraft.net

2. Find "Log in" button

3. Log in

4. Use Mojang account while logging in

5. ❌ Notice "Incorrect username or password" even though you are using Mojang account