macOS Monterey 12 - Couldnt Start Dropbox

Hi, Support --

I installed MacOS Monterey. Dropbox worked for a while, but now it won't start.

I saw an older, unresolved thread on a similar topic. Based on suggestions there, I quit DB, removed the app, followed the Advanced Installation instructions, e.g., to remove ~/.dropbox, then downloaded and reinstalled DB; no change. I'll paste the full info from the "Couldn't start Dropbox" popup below, but the important part seems to be at the tail of the log:

nucleus_python.NucleusSyncEngine.__cinit__
nucleus_python.SyncEngineError: "Initializing engine |>> Initializing filesystem |>> Attempting to register icons |>> fchflags syscall: _set_hidden |>> Permission denied"

I see that DB re-created ~/.dropbox, so it's not having any obvious permissions problem there. I can't tell what it's trying to do where to register icons, so I can't check permissions for the error it reports.

One more thing: I also run Google Drive app. However, DB and GD are syncing separate, non-overlapping directories: DB syncs ~/Dropbox; GD syncs ~/Pictures and ~/Google Drive

iMac, Monterey 12.0.1

freshly downloaded and advanced-installed dropbox.app

my background: Linux application software, Linux commands, familiar with shells and Linux command-line I/F in MacOS (Terminal)

bn.BUILD_KEY: Dropbox
bn.VERSION: 135.4.4221
bn.constants.WINDOWS_SHELL_EXT_VERSION: 51
bn.is_frozen: True
machine_id: a006ca99-0f98-5726-9038-3f97a8f5be7e
pid: 4029
ppid: 1
uid: 501
user_info: pwd.struct_passwd(pw_name='rob', pw_passwd='********', pw_uid=501, pw_gid=20, pw_gecos='Rob', pw_dir='/Users/rob', pw_shell='/bin/tcsh')
effective_user_info: pwd.struct_passwd(pw_name='rob', pw_passwd='********', pw_uid=501, pw_gid=20, pw_gecos='Rob', pw_dir='/Users/rob', pw_shell='/bin/tcsh')
euid: 501
gid: 20
egid: 20
group_info: grp.struct_group(gr_name='staff', gr_passwd='*', gr_gid=20, gr_mem=['root', '_serialnumberd', '_BGMXPCHelper'])
effective_group_info: grp.struct_group(gr_name='staff', gr_passwd='*', gr_gid=20, gr_mem=['root', '_serialnumberd', '_BGMXPCHelper'])
DYLD_LIBRARY_PATH: None
cwd: '/'
real_path='/'
mode=0o40755 uid=0 gid=0
parent mode=0o40755 uid=0 gid=0
HOME: '/Users/rob'
appdata: '/Users/rob/.dropbox/instance1'
real_path='/Users/rob/.dropbox/instance1'
mode=0o40700 uid=501 gid=20
parent mode=0o40755 uid=501 gid=20
dropbox_path: '/Users/rob/Dropbox'
real_path='/Users/rob/Dropbox'
mode=0o40700 uid=501 gid=20
parent mode=0o40755 uid=501 gid=20
sys_executable: '/Applications/Dropbox.app/Contents/MacOS/Dropbox'
real_path='/Applications/Dropbox.app/Contents/MacOS/Dropbox'
mode=0o100755 uid=501 gid=20
parent mode=0o40755 uid=501 gid=20
trace.__file__: '/Applications/Dropbox.app/Contents/Resources/python-packages.zip/dropbox/client/ui/common/boot_error.pyc'
real_path='/Applications/Dropbox.app/Contents/Resources/python-packages.zip/dropbox/client/ui/common/boot_error.pyc'
not found
parent not found
tempdir: '/var/folders/st/cnnvt94r8xj6qf001s6s66280000gn/T'
real_path='/private/var/folders/st/cnnvt94r8xj6qf001s6s66280000gn/T'
mode=0o40700 uid=501 gid=20
parent mode=0o40755 uid=501 gid=20
Traceback (most recent call last):
File "dropbox/client/main.pyc", line 822, in wrapper
File "dropbox/client/main.pyc", line 6574, in finish_dropbox_boot
File "dropbox/client/message_queue.pyc", line 313, in _wrapped
File "dropbox/client/main.pyc", line 6112, in _init_components_for_account
File "dropbox/client/main.pyc", line 6036, in create_sync_engine
File "dropbox/sync_engine_boundary/factory.pyc", line 226, in make_sync_engine
File "dropbox/sync_engine/nucleus/classic_client/sync_engine.pyc", line 280, in __init__
File "dropbox/sync_engine/nucleus/classic_client/modern_client/modern_client.pyc", line 248, in __init__
File "dropbox/sync_engine/nucleus/classic_client/modern_client/base.pyc", line 170, in __init__
File "dropbox/sync_engine/nucleus/classic_client/thin_adapter/in_proc.pyc", line 213, in __init__
File "dropbox/sync_engine/nucleus/classic_client/thin_adapter/in_proc.pyc", line 517, in _init_new_engine_locked
File "dropbox/sync_engine/nucleus/thin_client/client.pyc", line 133, in __init__
File "desktop/extensions/nucleus/nucleus_python.pyx", line 76, in nucleus_python.NucleusSyncEngine.__cinit__
nucleus_python.SyncEngineError: "Initializing engine |>> Initializing filesystem |>> Attempting to register icons |>> fchflags syscall: _set_hidden |>> Permission denied"