Readynas 104 can't see in network Windows 10

Good.

So what you have is a discovery problem, and not an access problem.  This problem tends to come and go (and some people here have found that when Windows updates itself the behavior seems to change).

There are two ways to proceed.

(a) you can work around the problem several different ways.  

-create one or more desktop shortcuts fo the NAS (or specific shares)

-add one or more network locations to file explorer (which would show up in the right pane).

-Map shares (or even the entire data volume) to a PC drive letter

(b) you can try to fix it. There are a couple of threads here from people who have managed to do that.  Though sometimes their solutions don't seem to work for others.

One thing you can/should check:  sometimes this happens because the windows workgroup setting in the NAS doesn't match the Windows 10 setting.  So check that at least.