Issue with NAS discovery after installing new modem/router

Until very recently I was using my 3-month old Samsung UE32D5000 TV, Ethernet wired to my Speedtouch modem/router driven LAN, in combination with my Synology DS-210j NAS server, and it all worked very well.
Because of my upgrade to VDSL2, I received a new modem/router from my provider, a ZTE H200n. The only that really changed in my LAN, is that I'm now in the 192.168.2.* range of IP-adresses in stead of 192.168.1.*. Not very exciting, I think.
Now all of a sudden the UE32D5000 won't detect the Synology anymore. The TV and the NAS both show up in the router, so why can't they see each other? I can see the NAS on all my other devices ... I installed PC Share Manager on my laptop, it detects both TV and NAS, and I can play contect from the NAS on my TV. I've already been checking all kinds of settings, both in the TV and in the NAS. I've even done a reset to factory settings on the UE32D5000, but to no avail. I've checked that the TV is connected not only to the LAN, but also to the Internet. I tested without the Ethernet switch I normally use, to eliminate that factor. I've swapped Ethernet ports on the router. I believe I've checked anything that can be checked. But still NAS not visible.
Hope that anyone can be of help. Very stupid issue: it worked fine, and only switch of modem/router spoils it.