MBL not visible in wifi network anymore

I want to kindly ask for your help.
For about one week my MBL stopped being visible to my wifi network. I have access to it through my PC with Windows 10 and I am able to see the dashboard and to ssh it.
Unfortunately I am not able anymore to stream files to my Smart TV or my phone from the same wifi network. I have to mention that I haven’t changed any settings in the router (TP Link Archer C7) or in the MBL before the MBL became invisible to my wifi network.
Thank you for your time.
Kind regards,

Hi, unplug and WD NAS drives from your network immediately!
Unfortunately you may well have suffered a global hack that has wiped your drive and done a factory re-set.
I and many others have had this occur.
If you can plug in direct to your pc with a ether net cable, rescan your network to see the NAS drive as per a new installation you can locate it and log in with admin username and no password.
Create a new user with password, then right click on the drive in an explorer window, “open” the drive, use new user & password, and you can see anything left on the drive.
Sadly it is probably wiped.
WD gave July only for people to find this security failure which they admit was their fault.
Basically they are washing their hands of it!
Sorry its not more positive.
I wish you well.
I lost everything.

Thank you for your explanation.
Apart from the hacking problem, I had issues with MBL accessing from internal network, after I disconnected it from the remote access.
The computer which has the direct Ethernet connection to the same router as MBL doesn’t have any problems accessing the MBL.
The other devices wirelessly connected to the router aren’t able to access the MBL.
Eventually, it turned out to be the wireless range extender that I use to connect those devices. After several restarts of the router and the range extender, I have the MBL visible from any device wired or wireless in the network.