Lost RDP access after EC2 instance type change

You’ve most likely changed from one family to another. Each family may have a different network adapter. You’ll have to revert this back and review the documentation before retrying.

It may be a case of installing the correct network drivers before retrying.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-resize.html

Please check this similar issue from a user some months ago: NLA error after updating instance type. After an instance change the ENI associated to that instance can be lost so you Network Layer Authentication will fail.

Check also the troubleshoot connect windows instance guide. Specially the section: Troubleshooting Remote Desktop issues using AWS Systems Manager, that shows you how to use AWS system manager to help you solve connections issues with your Windows instances.

If you still need help you can post here the error message that your are getting so we can understand better what is the issue.

If there are no problems around the network, it is possible that the RDP service is not running properly.
Please refer to the following document to check if the RDP service is running on EC2.
https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/troubleshoot-connect-windows-instance.html#Troubleshooting-Remote-Desktop-Connection-issues-using-AWS-Systems-Manager

Also check this document for other troubleshooting tips just in case.
https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/troubleshoot-connect-windows-instance.html