Bad Request / 503

I have an running nextcloud/docker in my homelab, working fine thru HAproxy

But with two new NextCloud in Proxmox (CT) I cant get them accessable thru the HAproxy, either I get the 503 Error or the following;

# Bad Request

Your browser sent a request that this server could not understand.
Reason: You’re speaking plain HTTP to an SSL-enabled server port.
Instead use the HTTPS scheme to access this URL, please.

The nextcloud sites works fine in the local network…

Whats wrong?