ERR_CONNECTION_REFUSED accessing PMG web interface or Exchange OWA from Chrome

HAProxy version 2.4.22-0ubuntu0.22.04.3

Proxmox Mail Gateway behind it.

All works fine, but suddenly started getting an error “ERR_CONNECTION_REFUSED” in any browser at some PCs of my copmpany. Some PCs works well howerever.
At the same time if i open the PMG by IP it works well.

Please help me resolve this issue or teach me please how to find the reason of that error?

Thanks in advance.

UPD: actually i have Exchange 2019 behind the Haproxy too. And from time to time some PCs can’t access OWA with the exactly same error.
Help needed. Thanks.


Any help?