You need valid user or server admin credentials to login. When you create a new Azure SQL database, it asks for setting server admin user and password. Please use the same to login.
In case you forgot the server admin password, you can reset it with help of below reference link.
Please "Accept the answer" if this helps or let me know more details about your scenario.
References:
Reset Server admin password for an Azure DB
single-database-create-quickstart