Unable to watch iTunes movies downloaded onto my WD MPWP on my iPad

Hi Techie Legends,
I purchased a WD My Passport Wireless Pro (MPWP) to store our iTunes movie library on it. I wanted the kids and ourselves to be able to watch movies on our iPads when we are travelling and camping without requiring any type of internet connection or cables. I can get the movies onto the MPWP and play them using Quicktime on my Mac mini desktop no probs. However when my iPad (Gen 5) is connected to the MPWP (wired or wireless) I am unable to play the same movies. The MPWP asks me if I want to download the .m4v movie file. I click Download. It downloads but will not open and play? I have tried the Plex app as instructed by the instructions within the MPWP but it comes up with- “Payback Error. This server is not powerful enough to convert video”. I did a search on what appeared to be similar topics that are a few years old now and there wasn’t fixes I could really understand. Any help would be greatly appreciated. Thanks and stay safe
Kev