Here you can check if you have a guest account. When you click Check a new page will open looking like this
I this is the first time you sign in to this service, you will be asked to consent to Nets using you name and profile information. That is necessary to be able to provide the users which you are collaborating with a minimum set of details to understand who they are sharing with.
You might already have used Multi Factor Authentication required by your own organisation. Nets requires that to, and we cannot see if you have already been validate before.
If you cannot log-on to the Nets Merchants Services IntraNets and get messages such as 'your account was not found', then you will have to create a Microsoft account using your company email address. That will have no impact on your current set-up, it is simply a technique used to ensure that we know that you have access to the mailbox.