No dialog box when connecting external HD?

Solved after a message to support - this worked for me

In order to help you with being unable to receive a notification for external drive backup, can you please relink your account? This is to ensure to refresh the data on your device.

1. Sign in to dropbox.com with one of the accounts you’d like to unlink.
2. Click your avatar (profile picture or initials) and select “Settings’
3. In the Security tab, under Devices, click on the trash can symbol for the device which is experiencing issues
4. Your Dropbox will then prompt you to re-enter your account information. Your account will then take a few moments to re-index your Dropbox folder, and sync any pending changes before returning to normal activity.

If you have any questions at all, Matt, please do not hesitate to email.

I'm on Windows 10. I was hoping to back up a 4TB Seagate external HD (NTFS formatted) to Dropbox. The Dropbox app was not offering me the option to back up the drive. I followed the steps in matsuli's post above to unlink my PC and my Dropbox account. Unfortunately, now the Dropbox app will not start. I get the following message:

"Couldn't start Dropbox.

This is usually because of a permissions error. Storing your home folder on a network share can also cause an error."

Then there is a link to a text file which contains the following:

bn.BUILD_KEY: Dropbox
bn.VERSION: 141.4.3299
bn.constants.WINDOWS_SHELL_EXT_VERSION: 52
bn.is_frozen: True
machine_id: ee043a44-2832-4b62-9ea2-384b83c353ea
pid: 8648
cwd: 'C:\\Program Files (x86)\\Dropbox\\Client'
real_path='C:\\Program Files (x86)\\Dropbox\\Client'
mode=0o40777 uid=0 gid=0
parent mode=0o40777 uid=0 gid=0
HOME: None
appdata: 'C:\\Users\\garet\\AppData\\Local\\Dropbox\\instance1'
real_path='C:\\Users\\garet\\AppData\\Local\\Dropbox\\instance1'
mode=0o40777 uid=0 gid=0
parent mode=0o40777 uid=0 gid=0
dropbox_path: None
not found
parent not found
sys_executable: 'C:\\Program Files (x86)\\Dropbox\\Client\\Dropbox.exe'
real_path='C:\\Program Files (x86)\\Dropbox\\Client\\Dropbox.exe'
mode=0o100777 uid=0 gid=0
parent mode=0o40777 uid=0 gid=0
trace.__file__: 'C:\\Program Files (x86)\\Dropbox\\Client\\141.4.3299\\python-packages.zip\\dropbox\\client\\ui\\common\\boot_error.pyc'
real_path='C:\\Program Files (x86)\\Dropbox\\Client\\141.4.3299\\python-packages.zip\\dropbox\\client\\ui\\common\\boot_error.pyc'
not found
parent not found
TMP: C:\Users\garet\AppData\Local\Temp
TEMP: C:\Users\garet\AppData\Local\Temp
tempdir: 'C:\\Users\\garet\\AppData\\Local\\Temp'
real_path='C:\\Users\\garet\\AppData\\Local\\Temp'
mode=0o40777 uid=0 gid=0
parent mode=0o40777 uid=0 gid=0
Traceback (most recent call last):
File "dropbox\client\authentication\register_host_helper.pyc", line 483, in _try_register_host
File "dropbox\client\authentication\register_host_helper.pyc", line 949, in handle_changed_host_secret
File "dropbox\sync_root\helpers.pyc", line 367, in destroy_root_from_config
AssertionError

I have tried restarting my PC and uninstalling / reinstalling the Dropbox app, but I keep getting the same message. I am not running any third party security software.

I'd really value any assistance with the above. I feel like I'm slipping backwards down a rabbithole...

Gareth