c# - element not visible Target invocation exception -

i trying automate login on dropbox https://www.dropbox.com/chooser ,but still facing issues element not visible, weird, though if page loaded successfully.

here code filling password:

   protected virtual void fillpassword(string password)     {         //password.clear();         password.sendkeys(password);     } 

the last line fails on target invocation exception. wanted use password.clear();, failing.

here locator password:

[cachelookup, findsby(how = how.name, using = "login_password")] protected override iwebelement password { get; set; } 

what going on? tried use wait methods page,but has not helped. know why crashes?

i changed html locator to:

[cachelookup, findsby(how = how.cssselector, using = ".text-input-wrapper    [name=\"login_password\"]")] protected override iwebelement password { get; set; } 

and works fine. not sure why name selector cannot find it. misunderstanding me. both approaches should work. here page source of field element:

<div class="text-input-wrapper"> <input id="pyxl14559" class="password-input text-input-input" type="password" name="login_password"> <label for="pyxl14559" style="">password</label> <small class="secondary-label"></small> <div class="password-caps-indicator">caps lock on</div> </div>