Dear Darce Blakely,
Hello! Welcome to the Microsoft Community.
It looks like you want to add your mother-in-law to your Microsoft 365 Family subscription. But you have some problems adding her? Maybe there are some prompts telling you that your account or computer is blocked?
I understand your feelings and I will do my best to help you solve this problem.
First of all, I have to mention that your question seems too broad and I can't pinpoint the problem you are experiencing. My current guess is that you get a message about being blocked after using your Microsoft account. If this is the case, you can go to the "private mode" of your browser and try again. For Edge, select the "..." menu in the upper right corner and select "New InPrivate Window".
Here are the steps on how to invite others to join your Microsoft 365 Family subscription:
Please refer to steps 1 and 2 in order:
Share your Microsoft 365 Family subscription - Microsoft Support
Also, please try to share more information about "Computer is blocked" with me. For example, after what steps did you encounter this problem? What is its full error message? It would be better if you can share pictures that can illustrate the problem.
Please pay attention to protecting your personal privacy. We can only provide you with technical assistance and have no right or ability to check your account. The community is an open platform, so be careful to prevent privacy information from being leaked.
Looking forward to your reply. My next reply may take some time. Thank you for your patience.
Wishing you and your family a Merry Christmas filled with joy and warmth!
Best Wishes
Pyke.D | Microsoft Community Support Specialist