No reachable EC2 Windows instance via rdp/ping (probably no connection)

Question

I get no connection to my EC2 Windows instance. I tried it over RDP and ping command. I checked the documentation and tried several points listed in the link below.

Link: https://docs.aws.amazon.com/en_en/AWSEC2/latest/UserGuide/TroubleshootingInstancesConnecting.html

I checked the security groups, the subnets, the internet gateway and the ACLs. In some cases I allowed all traffic, RDP and ICMP and I chose "anywhere" for the IP area.

I stopped and started the instance several times when I did this.

I tried to ping the instance with my company PC and with my private smartphone but it didn't work.

RDP connection still doesn't work.

Can you help me?

Thank you.