How are you accessing the media with the old TV and the PC? Using the MyCloud as a Media Server, or as a File Server? i.e. what application are you using to view media on the PC?
I’m going to assume that the old TV was accessing the MyCloud Twonky Media Server, using DLNA/UPnP, rather than accesing the file system directly.
Not familiar with either TV, but you might look for a ‘Search for UPnP/DLNA Server’ option in their menu.
You might also try setting the Media Receiver type in Twonky. See:
You may need to enable the receivers in the Twonky UI, too (so they’re allowed access). The default is to allow all devices to access, but you may have modified that setting.
[goes to read user guide for new TV. oh, there isn’t a detailed user guide; it’s on the device itself…]