new purchase won't synch with iPad!

I have the latest iTunes software running on the family Windows 7 Home Premium X64 desktop. It is connected to my no-longer-updateable iPad 1 running the latest version of iOs available via USB cable. I download all episodes of a recent purchase of Masterpiece Theater (Daunton Abbey season 3) intending to transfer it to my iPad just like I did with earlier downloads of the same series so I can watch it in bed with headphones while my husband sleeps. The transfer fails with a message indicating that the format is not supported. Then we tried streaming it over our 1000 mbps certified Ethernet network to our Apple TV. This worked just fine in the past. Now, all of a sudden, the new download "freezes" on screen when streamed to the Apple TV. Ouir Apple TV also refuses to install new versions of iOs! We have over $900.00 invested in this hardware alone, why has it suddenly stopped working on what seems to be a standard procedure that has been working to the better part of three years? Do we have to "back date" our iTunes software and re-download? We have 52 mbps wireless networking connected to the iPad 1. Is there a way to stream my purchase directly to the old iPad? We received a subscription to the Atlantic Magazine, but their app only runs on iOs 6 and won't install. Is there a work around for this probelm?