Jakub Serocki hi,
the system locks you out and then tells you to log in to get help. you do not need to access the azure portal to create a support ticket. microsoft has a dedicated page for people who cannot sign in. this is your way in. go to the azure support contact page. look for a link that says "i cannot sign in to my account" or "having trouble with your account". this is specifically designed for your exact scenario.
once you are on that page, you can fill out a form to create a support request without needing to log in. you will need to provide information to verify your identity, such as your email address, your azure subscription id if you have it, and any domain names associated with your tenant.
when you get a support agent on the line, explain clearly that your azure ad tenant was blocked due to inactivity and you need an administrator to reactivate it. they have the tools to do this on the backend.
this process of using the "cannot sign in" path is a universal workaround for any cloud platform when you are locked out.
so, use the "cannot sign in" option on the azure support page to bypass the login requirement and get a ticket opened. that is your direct line to the help you need.
rgds,
Alex