I don't believe it's the Roku. I use a DLNA server and if I exit RMP and restart it the list is always reloaded with the latest info. Since I have two DLNA servers on my network I can even back out of one, move to the other, then return to the first one and again the data is reloaded.
RMP does not maintain any local information from your DLNA server. It doesn't have any memory for that. It only lists what the DLNA server sends, assuming it is playable media. So unfortunately, your issue is the DLNA server software running on your router. I personally have never used a router based DLNA server because they don't have the power to transcode video, especially 4K material. And Roku has such limited codec support some sort of transcoding is almost always necessary with my media, even if it's just the audio.
The one thing that RMP does is not display media it doesn't think it can play. So if media that you know will play does't show, it's the DLNA server not presenting it accurately. If it was something that used to be displayed and now does not, my guess is an update of the DLNA server software might have changed something. I would have to see the media info of a file that doesn't display to know for sure why RMP might not display it. I can say that RMP sees all of my UHD BD movies I've ripped to my server. My DLNA server is only transcoding the audio, since no Roku device supports the lossless audio codecs. In fact, that might be your issue. Unsupported audio tracks, so it doesn't display. The only fix for that is to either remux your media with a Dolby Digital track as default or use a DLNA server that can transcode the audio. Almost no router-based DLNA servers have the power to transcode.
I know this is an older thread but I'm having very similar issues.
Just purchased the Ultra 2020 model.
Like it so far but DLNA to my NAS is horrible.
It's not the NAS (Terra-Master F220) as My Android phone and my laptop and tablet all have never had issues seeing and accessing files of this device.
The Roku Media file app. when first installed played one .MKV file I had in the Video's folder on the NAS.
Now it doesn't even see all the folders, It only goes up to the letter I (beginning letter).
I created a new folder with my name (Andy), it does not see that either.
I uninstalled the Media app on the NAS and removed and reinstalled the Roku Media channel and all is the same. What is up with this device of specifically this crazy app?
Thinking of maybe returning it and getting a Firestick,
@JAOROS as you've noted, the DLNA server on some NAS devices are kind of weak. RMP can only display what the DLNA server shows as available.
I don't know what brand of NAS you have, but you might check and see if there's another DLNA server available for your device. Serviio is available for QNAP and Synology NAS devices, and if you don't have one of those you might be able to find something else. RMP works just fine with most DLNA servers, but as you have seen not all play nicely.
And just as an aside, Fire TV devices have most of the same media support limitations of a Roku. VLC might be available, which is a pretty good player on many devices. Not certain if Kodi has an app that will install on one. Even though it's an Android device, there are still some app limitations compared to other Android devices.
I don't feel this is a DLNA NAS issue at all. All my other devices have absolutely no issue accessing files this way on the NAS.
It's a Terra-Master F220
It's a bit cumbersome but as a band-aide I might try and move files to a USB and play them that way. Silly to have to do this. Someone (developer?) needs to take a hard look at the Roku Media app.
Willing to work with whomever that maybe to make this a better channel.
I only have experience using RMP with Serviio as the DLNA server, but it works just fine. If I add content to the server, I just need to exit RMP and re-open it and my new media is shown.
I looked up your NAS, and I found a review that seems to identify the issue you're having. To quote:
The DLNA app, for example, wouldn’t automatically re-index new files pushed to the folders it was meant to be watching. The only way to get them noticed was to stop and restart the service, annoyingly.
So it does seem to be a DLNA server limitation of your NAS, unfortunately.
That must be an old article. Like i stated, I have no issues via multiple PCs, Android phone or tablet.
Thanks for researching though...