Subdomain web page 503 Service Unavailable

Suddenly when I try to access to subdomain web page I get this error, main domain web page works.

503 Service Unavailable

No server is available to handle this request.
I am really bad with this kind of proxy especially because it is on opensense.
So I don’t know what more to check and what to do. Can aynone help me?
here is config file

When I check logs in haproxy I found this.
2024-06-05T08:02:30 Error haproxy 199.45.154.66:35026 [05/Jun/2024:08:02:29.368] smtps_front/0.0.0.0:465: SSL handshake failure (error:0A00018C:SSL routines::version too low)

2024-06-05T08:02:26 Error haproxy 199.45.154.66:34982 [05/Jun/2024:08:02:25.972] smtps_front/0.0.0.0:465: SSL handshake failure (error:0A000102:SSL routines::unsupported protocol)
2024-06-05T08:02:22 Error haproxy 199.45.154.66:43952 [05/Jun/2024:08:02:20.562] smtps_front/0.0.0.0:465: SSL handshake failure (error:0A000102:SSL routines::unsupported protocol)