Ad free has nothing to do with the issue. I suspect what is happening is that your account has been migrated to the new email system called outlook mail that all users are being migrated to.
You can verify this, if it says outlook mail (or outlook email) it is the new system.
As a first step to resolve the issue I would clear the browser cache/cookies
If you are using a browser to access your mail more often than not you can fix the problem you are having by clearing all the cache and cookies in your specific browser
*For Internet Explorer browser & MSN Butterfly: Press CTRL+SHIFT+DEL simultaneously and click Delete
*For Google Chrome: Press CTRL+SHIFT+DEL simultaneously and click Clear Browsing Data
*For Firefox: Press CTRL+SHIFT+DEL simultaneously and click Clear Now
*For Edge they are in settings (three dots>history>clear all settings)
(other browsers are similar)
If clearing the cookies & cache cache doesn't help answer these.
In order to help you effectively we need to know exactly what email system you are using. You can see the differences
here
Are you having problems accessing other accounts on the same computer?
Does the same problem exist when you use a different browser?
Does the issue persist on other computers?