Cannot mount with sshfs

I have built sshfs snap. below is snapcraft.yaml:

apps:
  sshfsd:
    adapter: full
    command: bin/start.sh
    command-chain:
      - bin/startup-env-var.sh
    environment:
      LD_LIBRARY_PATH: $SNAP/lib:$SNAP/usr/lib:$SNAP/lib/${SNAPCRAFT_ARCH_TRIPLET}:$SNAP/usr/lib/${SNAPCRAFT_ARCH_TRIPLET}
    daemon: simple
    restart-delay: 10s
    passthrough:
      install-mode: disable
    plugs: [network, network-bind, ssh-keys, home, fuse-support]

  sshfs:
    adapter: full
    command: usr/bin/sshfs
#    command: bin/sshfs
    environment:
      LD_LIBRARY_PATH: $SNAP/lib:$SNAP/usr/lib:$SNAP/lib/${SNAPCRAFT_ARCH_TRIPLET}:$SNAP/usr/lib/${SNAPCRAFT_ARCH_TRIPLET}
    plugs: [network, network-bind, ssh-keys, home, fuse-support]

parts:
  version:
    plugin: nil
    source: snap/local
    override-pull: |
      cd $SNAPCRAFT_PROJECT_DIR
      GIT_VERSION=$(git describe --tags --abbrev=0 | sed 's/v//')
      if [ -z "$GIT_VERSION" ]; then
        GIT_VERSION="0.0.0"
      fi
      snapcraftctl set-version ${GIT_VERSION}

  config-common:
    plugin: dump
    source: snap/local/runtime-helpers

  sshfs-start:
    plugin: dump
    source: sshfs
    stage-packages: [ sshfs ]

  config:
    plugin: dump
    source: config

Then, I install this sshfs snap with devmode. bin/start.sh will execute $SNAP/usr/bin/sshfs xxx@127.0.0.1:/var/xxx $SNAP_DATA/tmp/xxx -o reconnect,ServerAliveInterval=5,ServerAliveCountMax=3,idmap=user,allow_other -o IdentityFile=/var/snap/isimple-sshfs/common/.ssh/id_rsa

execute sshfs with -d, it outputs:

2021-12-01T15:32:44+08:00 isimple-sshfs.sshfsd[213998]: FUSE library version: 2.9.7
2021-12-01T15:32:44+08:00 isimple-sshfs.sshfsd[213998]: nullpath_ok: 0
2021-12-01T15:32:44+08:00 isimple-sshfs.sshfsd[213998]: nopath: 0
2021-12-01T15:32:44+08:00 isimple-sshfs.sshfsd[213998]: utime_omit_ok: 0
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]: unique: 2, opcode: INIT (26), nodeid: 0, insize: 56, pid: 0
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]: INIT: 7.33
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]: flags=0x13fffffb
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]: max_readahead=0x00020000
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]:    INIT: 7.19
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]:    flags=0x00000011
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]:    max_readahead=0x00020000
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]:    max_write=0x00020000
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]:    max_background=0
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]:    congestion_threshold=0
2021-12-01T15:32:45+08:00 isimple-sshfs.sshfsd[213998]:    unique: 2, success, outsize: 40

unique: 2, opcode: INIT (26) has successed. It maybe hangs up on unique: 4, opcode: ACCESS

And, error in dmesg log:

[37494.242201] audit: type=1400 audit(1638343963.100:12365): apparmor="ALLOWED" operation="open" profile="snap.isimple-sshfs.sshfsd" name="/home/liqing/Downloads/fstab.txt" pid=213858 comm="start.sh" requested_mask="r" denied_mask="r" fsuid=0 ouid=1000
[37494.244355] audit: type=1400 audit(1638343963.100:12366): apparmor="ALLOWED" operation="open" profile="snap.isimple-sshfs.sshfsd" name="/dev/fuse" pid=213886 comm="sshfs" requested_mask="wr" denied_mask="wr" fsuid=0 ouid=0
[37494.244367] audit: type=1326 audit(1638343963.100:12367): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=snap.isimple-sshfs.sshfsd pid=213886 comm="sshfs" exe="/snap/isimple-sshfs/x9/usr/bin/sshfs" sig=0 arch=c000003e syscall=165 compat=0 ip=0x7f9e1fe8225a code=0x7ffc0000
[37494.244369] audit: type=1400 audit(1638343963.100:12368): apparmor="ALLOWED" operation="mount" info="failed mntpnt match" error=-13 profile="snap.isimple-sshfs.sshfsd" name="/var/snap/isimple-sshfs/x9/tmp/device-modbus/" pid=213886 comm="sshfs" fstype="fuse.sshfs" srcname="liqing@127.0.0.1:/var/snap/edgexfoundry/current/secrets/core-data" flags="rw, nosuid, nodev"
[37494.249894] audit: type=1400 audit(1638343963.104:12369): apparmor="ALLOWED" operation="open" profile="snap.isimple-sshfs.sshfsd" name="/etc/ssh/ssh_config" pid=213889 comm="ssh" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
[37494.249903] audit: type=1400 audit(1638343963.104:12370): apparmor="ALLOWED" operation="open" profile="snap.isimple-sshfs.sshfsd" name="/etc/ssh/ssh_config.d/" pid=213889 comm="ssh" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
[37494.258648] audit: type=1400 audit(1638343963.112:12371): apparmor="ALLOWED" operation="open" profile="snap.isimple-sshfs.sshfsd" name="/root/.ssh/known_hosts" pid=213889 comm="ssh" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
[37494.264913] audit: type=1400 audit(1638343963.120:12372): apparmor="ALLOWED" operation="open" profile="snap.isimple-sshfs.sshfsd" name="/root/.ssh/known_hosts" pid=213889 comm="ssh" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
[37495.660827] audit: type=1326 audit(1638343964.520:12373): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=snap.isimple-sshfs.sshfsd pid=213886 comm="sshfs" exe="/snap/isimple-sshfs/x9/usr/bin/sshfs" sig=0 arch=c000003e syscall=166 compat=0 ip=0x7f9e1fe81757 code=0x7ffc0000
[37495.660833] audit: type=1400 audit(1638343964.520:12374): apparmor="ALLOWED" operation="umount" profile="snap.isimple-sshfs.sshfsd" name="/var/snap/isimple-sshfs/x9/tmp/device-modbus/" pid=213886 comm="sshfs"