Sole Microsoft 365 admin locked out – Authenticator MFA not working, unable to access Admin Center

I will answer you in English based on your previous message. As a friendly suggestion, posting in Swedish may help your question reach a wider audience and increase the chances of receiving assistance from other community members. 

Hi Peter Diephuis

When you contact Microsoft Support via phone service number to recover admin access via Customer service phone numbers - Microsoft Support, the first step is to provide an automated voice response from AI. Be careful, you won't be able to speak to a support representative if you don't respond appropriately here. 

Here's an example of a response that actually led to a support representative. you can refer to it:

Q. Can you tell me if you are calling as a home user who uses a product or service at home or a business user who uses it in your business to provide the best assistance? 
A.I am a business user. 
Q. Thank you. Can you give me the details of your inquiry? 
A. Login technical support. 
Q. First of all, can you tell me which products you are inquiring about today? 
A. Microsoft 365 business Standard。 
Q. Please wait a moment, I understand Microsoft 365. Are you calling about a new case or an existing one? 
A. New. 
Q. To receive phone support, your phone number must be associated with your Microsoft 365 admin profile. To do this, go to aka.ms/m365profile. Again, it aka.ms/m365profile . This can take 48 hours. In the meantime, you can go to aka.ms/m365profile and file a case online. If you prefer, you can also text the link to the phone number you are calling. What do you think? 
A. The phone number is already linked to the link. 
Q. Can you tell me about the products in your inquiry? 
A. Microsoft 365 Business Standard. 
Q. Are you a Global Administrator? 
A. That's right. 
Q. I'm sorry. I didn't understand. Are you a global administrator for your domain? 
A. Yes, I am a global administrator for the domain. 
Q. If you have any inquiries, you can contact a Microsoft representative. Are you sure? 
A. Yes. Please. 
Q. Yes, I understand. Please wait a moment.

Please note that this team is always overwhelmed, so you might need to wait for them to call you, this should take 3-10 working days. and in most countries/regions, billing support for Microsoft 365 for business products and services is provided in English from 9 AM-5 PM, Monday through Friday. Local language support varies by country/region.

In case the phone line is not supportive, you can consider directly submitting a support request via trial tenant as a helpful workaround:   

• Create a temporary Microsoft 365 tenant using a trial license: Go to https://www.microsoft.com/microsoft-365/business/microsoft-365-plans-and-pricing?msockid=2c66e4104dbb699a20faf2214cde687d and click Try for free to set up a temporary Microsoft 365 tenant with a trial license. 
• Use this new account to sign in to the Microsoft 365 Admin Center and submit a support request on behalf of your primary (locked) account.   
• Select the Help & support (headset) icon. If Support Assistant is enabled, turn it off > Type contact support in the search box > Select Contact support, then choose Phone or Email to submit your request.   

Note: This method doesn't require you to use your new account for your business. Instead, it allows you to create a temporary global administrator account so you can submit a support request, as your original global administrator account is locked out due to issues with multi-factor authentication. The trial account is free for one month. Be sure to delete it after submitting your support request to avoid any automatic renewals or charges from Microsoft.     

For further instructions, you can follow this guide: Get support - Microsoft 365 admin | Microsoft Learn.   

I hope this information helps.