Hi Kim,
According to your description, you have a work email account associated with a business subscription and you use the account to sign up for another personal subscription. Since these two subscriptions belong to different families, there can be some interference.
Although that two subscriptions are in one account is not the best practice for Office 365, I recommend you change the alias name of your personal account so that you can login to the portal with a different combination of user name and password.
Best Regards,
Jeremy Ren