AWS Load Balancer, enable listener for HTTPS and route to 80 - node.js

Question

I've an AWS LoadBalancer in front of two servers running SailsJS with PM2. The LB works very well and routes the incoming HTTP requests to the server, which is perfect.
Now, I need to add support for HTTPS, so I followed this guide:
AWS Create a Classic Load Balancer with an HTTPS Listener, using a self-generated SSL certificate, and used this configuration for the ports
LB Port 80 - Instance 80
LB Port 443 - Instance 80
And the security group has these ports opened:
22,
80,
443
So, if I understood correctly, the LB will receive the HTTPS request on port 443 and will forward it to port 80 of the instance. My instance, of course, is listening on port 80.
The problem is, this don't work! I can make HTTP requests to the LB and all is routed perfectly to the Sails instance and the response is perfect. But if I use exactly the same URL but with HTTPS, then it doesn't work and I get a "ERR_SSL_PROTOCOL_ERROR".
What am I doing wrong, what am I missing?
Thank you!
EDIT 1
This is what I get if I try curl -v https://example.com
* Trying xx.xx.xx.xx...
* Connected to example.com (xx.xx.xx.xx) port 443 (#0)
* Unknown SSL protocol error in connection to example.com:-9838
* Closing connection 0
curl: (35) Unknown SSL protocol error in connection to mydomain.com:-9838
EDIT 2
Found another thread which suggested a different way of creating the certificate. So I tried it, but now AWS don't even accept the private key and the certificate
Server Certificate not found for the key: arn:aws:iam::111111111:server-certificate/CertificateMyName
EDIT 3
OK, so found more info on why I couldn't load the certificates to AWS and after trying some times, I managed to load it and use it.
After these, it appears to be working (with the warnings that is not a valid cert and bla, bla, bla, which is expected)
* Trying XXX.XXX.XXX.XXX...
* Connected to example.com (XXX.XXX.XXX.XXX) port 443 (#0)
* SSL certificate problem: Invalid certificate chain
* Closing connection 0
curl: (60) SSL certificate problem: Invalid certificate chain
So it appears to be working, and it appears, as #MarkB suggested that the certificate was wrong. Using the info found on EDIT 2, I created a new one, and upload it (with the info of EDIT 3) and it appears to be working.
I'll perform more tests to make 100% sure that this works and will report back soon.

Answer 1

Ok, so the problem was a wrongly generated certificate. I used the first method I found and it wasn't working, so just use these:
openssl genrsa -out client-key.pem 2048
openssl req -new -key client-key.pem -out client.csr
openssl x509 -req -in client.csr -signkey client-key.pem -out client-cert.pem
Even after that, AWS told me:
Server Certificate not found for the key: arn:aws:iam::111111111:server-certificate/CertificateMyName
But the last error is wrong, even with the error the certificate WAS added to the ACM, and I used it in my HTTPS 443 listener, tested again the services and all was working. So just create the certificate with the instructions above, import it in ACM and if it gives you an error like above, just ignore it, your cert will be on place and ready to use.
Hope this helps others!