EC2 system upgrade to nitro error

It's not clear from your question what has happened here. If this is a production issue, please contact our support team. re:Post is staffed by volunteers and we have no access to your account details. The support team is there to help and can access your account details and find out specifically what is wrong.

In this case: If you have switched from one instance type to another (I'm inferring that from the title of the question) then why not switch back to the old instance type?