Hi @Normancssmi,
My name is Gwen, and I would be happy to assist. What you are most likely running into with adding devices to Systems Manager is Enrollment authentication this setting can be found under Systems Manager > General page. For your protection, this is automatically enabled on all new Networks, and the enrollment authentication method defaults to "Managed: Use Meraki hosted accounts." These accounts are created under your Systems Manager Owners page.
https://documentation.meraki.com/SM/Device_Enrollment/SM_Enrollment_Authentication
https://documentation.meraki.com/SM/Other_Topics/Owners
Meraki Support's recommendation is to have enrollment authentication setting enabled in all dashboard networks, as this protects your network from having just anyone from enrolling devices. However, if you would like while you are actively enrolling devices the Enrollment authentication setting can be disabled and re-enabled when you are done.
Please let me know if you have any further questions or if there is anything that I can clarify.
If you found this post helpful, please give it Kudos. If my answer solves your problem, please click Accept as Solution so others can benefit from it.