Hi ​@Wormsek, 

Welcome to Box Community, and we’ll help setup the Multi-Factor Authentication in your account! 

First, use your alternate browser and/or clear your browser’s cache and cookies then proceed in setting up your MFA. 

To enable authentication app multi-factor authentication for your individual account:

1. Go to Account Settings > Account.
2. In the 2-Step Verification section, click Set Up. (Note: You will not see this section if your organization uses single sign-on (SSO) for authentication.)
3. Select Authentication App (recommended) and click Next.
4. Open the authentication app on your phone and scan the QR code. (You can also enter the secret key located under the QR code into the authenticator app manually.)
5. Enter the code you received in the authenticator app and click Submit.
6. Enter a phone number for verification, which would be used by Box support to verify your identity in the case where you are not able to authenticate in the app, and click Submit.
7. Copy the backup codes. Once copied, paste them into a file only you have access to and save the file somewhere secure. 
8. Click Complete.

To enable email multi-factor authentication for your individual account:

1. Go to Account Settings > Account. 
2. In the 2-Step Verification section, click Set Up.
3. Click Set Up.
4. Select Email and click Next.
   • The following window confirms you’ll use email MFA to sign in. Click Submit to continue.
5. Select the email you’d like to use for the Box login.
6. Enter the code sent to the email you selected for MFA.

After setting up MFA with your email, you're notified that email MFA is required the next time you login.

To enable SMS multi-factor authentication for your individual account:

Note

Your Box administrator may not allow SMS as an authentication method. If so, this option will not be available to you.

1. Go to Account Settings > Account.
2. In the 2-Step Verification section, click Set Up.
3. Select SMS Text Message and click Next.
4. Enter your phone number and click Continue. Some countries do not support 2FA via SMS.
5. Enter the code you received as a text message and click Submit.
6. Copy the backup codes. Once copied, paste them into a file only you have access to and save the file somewhere secure.
7. Click Complete.

Hope it works, and please let us know how it goes. 

Hi.
Incognito mode helped. 

But honestly saying to the user to clean his cookies is not good support. I’m using my cookies to many other sites and don’t want to clean them only because I have problem with Box website :/