Issue Description
When accessing Portainer via the web you may receive the following error message:
Client sent an HTTP request to an HTTPS server.
Cause
This error occurs when you attempt to access Portainer's HTTPS URL (port 9443) using the HTTP protocol:
http://my.portainer.url:9443/
This is because port 9443 only accepts the HTTPS protocol and does not accept HTTP requests.
Resolution
Use the HTTPS protocol in the address when accessing port 9443.
https://my.portainer.url:9443/
Alternatively if you have HTTP access enabled you can access via HTTP on port 9000:
http://my.portainer.url:9000/