In tcp_output function:
if (lwip_ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > wnd) {
    ....
    goto output_done;
}

In tcp_slowmgr function:
if (pcb->rtime >= pcb->rto) {
    pcb->cwnd = pcb->mss;
    tcp_rexmit_rto_commit(pcb);
}

tcp_rexmit_rto_commit ≈ tcp_output;

in tcp_output, The printf command output is as follows:
lwip_ntohl(seg->tcphdr->seqno) = 405161
pcb->lastack = 403701
seg->len = 1460
pcb->snd_wnd 65535
pcb->cwnd = 1460
so tcp_output will not send this tcp segment, It enters the slow start phase of congestion control and cannot exit.
Although unack data exists, the value of snd_wnd is 65535. lwip cant send data is correct this moment?