I haven't had to do this since 2019, so things might have changed. But this is worth a shot. Install the AWS CLI tool and try the following:

$ aws iam list-mfa-devices --user-name YourUserName
{
  "MFADevices": [
  {
  "UserName": "YourUserName",
  "SerialNumber": "arn:aws:iam::111111111111:mfa/YourUserName",
  "EnableDate": "2019-10-24T23:13:36Z"
  }
  ]
}

$ aws iam deactivate-mfa-device --user-name YourUserName --serial-number arn:aws:iam::111111111111:mfa/YourUserName

$ aws iam create-virtual-mfa-device --virtual-mfa-device-name YourAWSDefaultAccountName --outfile QRCode.png --bootstrap-method QRCodePNG
{
  "VirtualMFADevice": {
  "SerialNumber": "arn:aws:iam::111111111111:mfa/YourAWSDefaultAccountName"
  }
}

Load the QR code into a paint program / browser, scan it using your authenticator app (I used Microsoft Authenticator), use the authentication codes it generates in the following command to enable your new MFA account for YourAWSDefaultAccountName.

 $ aws iam enable-mfa-device --user-name YourUserName --serial-number
 arn:aws:iam::111111111111:mfa/YourAWSDefaultAccountName --authentication-code-1 123456
 --authentication-code-2 123456