'The Network Path Was Not Found': Synology DS215j

[Autobahn]

Dell Windows 8.1

I am not a computer expert so could terms be kept as simple as possible. Thank you.

A couple of days ago (after 3 years being able to connect) I was unable to connect to my Nas. Under 'Network Locations' on my laptop I have two folders for my DS215j:
One for Music Z:
One for Video Y:

I cannot even signin to my Nas drive using my browser?

I haven't a clue where to start to try and solve this.

 

[Autobahn]

It seems to have sorted itself out.
Haven't a clue how.
Yesterday I restarted the Nas and my laptop and I still could not connect to the Nas.
I have been trying some Google search recommendations and when they didn't work, putting the settings back to what they were.
Perhaps that reset something?
I decided to restart the laptop and Nas again, and this time everything worked as before.
But will this happen again?