Yes, is a fresh install, with your guide installation, I bought iredadmin pro today, Three installation and all have the same error.

I found the problem
in the next file

/etc/fail2ban/jail.d/nginx-http-auth.local
the log path is empty

so I don't know if the path is /var/log/nginx/error.log

Thanks

in centos 7 this is the content of the file

[nginx-http-auth]
enabled     = true
filter      = nginx-http-auth
action      = iptables-multiport[name=nginx, port="http,https,smtp,submission,465,pop3,pop3s,imap,imaps,sieve", protocol=tcp]
logpath     = /var/log/nginx/error.log

In debian I only change log path same to centos but que I try to enter with round cube or solo my ip is inmadiatly blocked

adminit@mail001:~$ sudo nft list ruleset
table inet filter {
    set f2b-roundcube {
        type ipv4_addr
        elements = { 186.155.208.254 }
    }

    set f2b-postfix {
        type ipv4_addr
        elements = { 91.134.145.129 }
    }

    chain input {
        type filter hook input priority 0; policy accept;
        tcp dport { smtp, http, pop3, imap2, https, urd, submission, imaps, pop3s, sieve } ip saddr @f2b-postfix reject
        tcp dport { smtp, http, pop3, imap2, https, urd, submission, imaps, pop3s, sieve } ip saddr @f2b-roundcube reject
        iif "lo" accept
        ct state established,related accept
        ip6 nexthdr ipv6-icmp icmpv6 type { destination-unreachable, packet-too-big, time-exceeded, parameter-problem, mld-listener-query, mld-listener-report, mld-listener-done, nd-router-solicit, nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert, ind-neighbor-solicit, ind-neighbor-advert, mld2-listener-report } accept
        ip protocol icmp icmp type { destination-unreachable, router-advertisement, router-solicitation, time-exceeded, parameter-problem } accept
        ip protocol igmp accept
        ip protocol icmp icmp type echo-request limit rate over 10/second burst 4 packets drop
        ip6 nexthdr ipv6-icmp icmpv6 type echo-request limit rate over 10/second burst 4 packets drop
        tcp dport ssh accept
        tcp dport http accept
        tcp dport https accept
        tcp dport smtp accept
        tcp dport submission accept
        tcp dport pop3 accept
        tcp dport pop3s accept
        tcp dport imap2 accept
        tcp dport imaps accept
        counter packets 326 bytes 28045 drop
    }

    chain output {
        type filter hook output priority 0; policy accept;
    }

    chain forward {
        type filter hook forward priority 0; policy drop;
    }
}