I appreciate all your efforts!

Edited the profile, restarted the service. Tried a variety of video formats. By the way, I'm using the latest beta version of the Roku player. Also, this is using my Serviio testing PC, not my main server. It has about half the power (2 vs 4 core and lower CPU power).
online (Crackle): plays, looks and sounds good
SD MPG: good
SD MKV: good
SD WTV: good
SD AVI: good
SD MP4: good
HD MP4: mixed. I have one at 720p that would play, but several others at 1080p won't even attempt to load
All other HD (MPG, MKV & WTV, 720 & 1080p) won't even load. The strange thing is that many of these HD files will play through Chaneru. I do have issues there as well, however, so it may be related to how they were ripped and converted to MP4.
I've been using MakeMKV for over a year, and there has been numerous updates during that time. If I ripped something with an older verson, there may have been issues. I can't even remember what program I used to convert to MP4. I tried Handbrake once, but couldn't believe how long it took. Even with my limited Blu Ray collection, it would take me weeks to convert them all. Besides, I finally have a player that will play MKV natively, and my BDs (using FLAC for the audio) sound and look as good as the disc. I still want the Roku to work well, though. Besides the two I have, my daughter and son-in-law have one and they want me to build them a Serviio box.
Dan
LG NANO85 4K TV, Samsung JU7100 4K TV, Sony BDP-S3500, Sharp 4K Roku TV, Insignia Roku TV, Roku Ultra, Premiere and Stick, Nvidia Shield, Yamaha RX-V583 AVR.
Primary server: AMD Ryzen 5 5600GT, 32 gig ram, Windows 11 Pro, 22 TB hard drive space | Test server: Intel i5-6400, 16 gig ram, Windows 10 Pro
HOWTO: Enable debug logging HOWTO: Identify media file contents