Dear Lizandra,
Greetings! Thank you for posting in Microsoft forum.
The error you mentioned means that you don't have an Office 365 (or Microsoft 365) plan that includes Microsoft 365 Apps and that supports shared computer activation. Therefore, you can't use shared computer activation.
But based on your post, I understand you have Microsoft 365 Business Premium plan which includes Microsoft 365 Apps for business, and it includes support for shared computer activation.
- Note*: The Microsoft 365 Business Premium plan is the only business plan that includes support for shared computer activation. There are other business plans, such as Microsoft 365 Business Standard, that include Microsoft 365 Apps for business, but those business plans don't include support for shared computer activation.*
Make sure you assign each user a license for Microsoft 365 Apps and that users sign in the shared computer with their own user account.
There are three options to enable Shared computer activation. I noticed you have tried two options (1) using Registry Editor (2) using the Microsoft Support and Recovery Assistant. May I suggest the third option, using group policy? Reference: Use Group Policy to enable shared computer activation
Further, you can also consider enabling shared computer activation during the initial installation of Microsoft 365 Apps, you can instruct the Office Deployment Tool to do so during installation. When you're using the Office Customization
Tool at config.office.com or the wizard built into Microsoft Configuration Manager, make sure that you enable the option Shared Computer in the Product activation section.
If my understanding above is not consistent with yours, you can also post back and point that out.
Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!
Sincerely,
Neha | Microsoft Community Moderator