We are a volunteer organization, members change yearly or every two years.... how to delete all previous users including administrators who no longer are group members?

Do you have any access as the Primary Admin?

Hi sandra_v2!

Fiat Lux - ASIA is correct. You have must logged in as either the Primary or Master admin to be able to delete users. Just a heads up, you'll have to manually delete them on your QuickBooks Online account. Let me guide you how:

1. Click the Gear icon.
2. Under Your Company, select Manage users.
3. Locate the name and click the Edit drop-down.
4. Select Delete.
5. firm you want to delete the user by selecting Delete again.

Afterwards, you can add new users. Here's a reference as your guide:  How to add, delete, or change a user's access.

That should help you delete a user in QBO. Please let me know how it goes or if I can be of additional assistance.