I'll try to help out.    I think it depends on the browser you are using and the settings you have.    You may have the browser set to erase history when you close. That would log you out each time. 

Then, depending on operating system it may ask if you want to "save " a "secure" password and then makes up its own for you and will only work on that system. 
For example If I let my apple device save a secure pwd, then my I can't get in on Windows and vice versa.   When I have to update ( when I access from a different IP)  I log out and log in with my saved pwd.  if I just hit update, if saves the secure gobblydegook  and I have to start from scratch. 

So  how to fix.....
If you save passwords on your browser, check to see you have the latest one saved. 

If you need to change it to get in just make sure that it is saved.  Or if you can't get in, let me know and we'll try something else. 


ps  Also check the little box below your user name  to keep you logged in