sftp: "File does not exist" when copying remote file - SFTP client

I really wanted this to be a last resort, but I’m at my wits end trying to figure this out. My code is at the bottom. The main error I keep getting when using the typical configuration is “file does not exist.” WinSCP has no issues.

Things I’ve tried:

1. Attempted the same operation using RClone to make sure my code is not the issue (see https://forum.rclone.org/t/sftp-remote-to-local-copy-failed-to-copy-file-does-not-exist/14414/2). RClone fails with the “File does not exist” error.

2. sftp.NewClient(conn) with sftpClient.Open(srcInvPath) - Received the error: “File does not exist”

3. sftp.NewClient(conn, sftp.MaxPacket(20480)) with sftpClient.OpenFile(srcInvPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC) - Received the error: “read from 13 for 20480 from 20497 not supported. (SSH_FX_FAILURE)”

4. sftp.NewClient(conn) with sftpClient.OpenFile(srcInvPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC) - Received the error: “read from 13 for 32768 from 32785 not supported. (SSH_FX_FAILURE)”

5. sftp.NewClient(conn) with sftpClient.OpenFile(srcInvPath, 0700) - Received the error : “EOF”. Have no idea why I tried this.

package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/pkg/sftp"
	"golang.org/x/crypto/ssh"
)

var invImpRootPath = "C:\\Invoices\\"
var invImpErrPath = filepath.Join(invImpRootPath, "Errors")
var invImpProcPath = filepath.Join(invImpRootPath, "Processed")
var invRegExp = regexp.MustCompile(`(?m)^(Invoice)\.([0-9]*)\.([0-9]*)\.([0-9]{1,5})\.xml$`)
var sftpInvPath = "/Invoices/outbound"

func main() {
	err := os.MkdirAll(invImpRootPath, os.ModeDir)
	if err != nil {
		fmt.Printf("Error creating Invoices directory: %s", err.Error())
		panic(err)
	}

	err = os.MkdirAll(invImpErrPath, os.ModeDir)
	if err != nil {
		fmt.Printf("Error creating Errors directory: %s", err.Error())
		panic(err)
	}

	err = os.MkdirAll(invImpProcPath, os.ModeDir)
	if err != nil {
		fmt.Printf("Error creating Processed directory: %s", err.Error())
		panic(err)
	}

	user := {removed}
	pass := {removed}
	host := {removed}
	port := "22"

	hostKey := getHostKey(host)
	config := &ssh.ClientConfig{
		User: user,
		Auth: []ssh.AuthMethod{
			ssh.Password(pass),
		},
		HostKeyCallback: ssh.FixedHostKey(hostKey),
	}

	conn, err := ssh.Dial("tcp", host+":"+port, config)
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	sftpClient, err := sftp.NewClient(conn, sftp.MaxPacket(20480))
	if err != nil {
		log.Fatal(err)
	}
	defer sftpClient.Close()

	files, err := sftpClient.ReadDir(sftpInvPath)
	if err != nil {
		log.Fatal(err)
	}

	for _, file := range files {
		srcInvPath := path.Join(sftpInvPath, file.Name())
		dstInvPath := filepath.Join(invImpRootPath, file.Name())

		dstFile, err := os.Create(dstInvPath)
		if err != nil {
			log.Fatal(err)
		}
		defer dstFile.Close()

		srcFile, err := sftpClient.OpenFile(srcInvPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC)
		if err != nil {
			log.Fatal(err) 
		}

		bytes, err := io.Copy(dstFile, srcFile)
		if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%d bytes copied\n", bytes)

		err = dstFile.Sync()
		if err != nil {
			log.Fatal(err)
		}
	}
}

func getHostKey(host string) ssh.PublicKey {
	// parse OpenSSH known_hosts file
	// ssh or use ssh-keyscan to get initial key
	file, err := os.Open("known_hosts")
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	var hostKey ssh.PublicKey
	for scanner.Scan() {
		fields := strings.Split(scanner.Text(), " ")
		if len(fields) != 3 {
			continue
		}
		if strings.Contains(fields[0], host) {
			var err error
			hostKey, _, _, _, err = ssh.ParseAuthorizedKey(scanner.Bytes())
			if err != nil {
				log.Fatalf("error parsing %q: %v", fields[2], err)
			}
			break
		}
	}

	if hostKey == nil {
		log.Fatalf("no hostkey found for %s", host)
	}

	return hostKey
}

Server information from WinSCP:

Thank you!