The number of Bitrix24 administrators depends on your plan. Therefore, when changing a plan, you maybe need to change the number of active administrators.
Go to Company > Employees section and search for administrators in the filter. If there is no Administrator field in the filter, add it manually using the Add Field section.
The list of active administrators will appear. Click on the name and go to the employee's profile.
Choose Revoke admin permissions in the Administrator menu.
If your Bitrix24 is blocked due to exceeding the number of administrators, you can delete some of them only after you renew your commercial plan or switch to another one. The Plan compatibility check will help you to choose the right variant.