It's hard to explain how difficult it is to install JMRI (https://jmri.org) and keep it running over an extended period of years. The good news is that it exists, is free, and keeps getting updated with data on all the new decoders that manufacturers produce, as well as many other amazing features and uses. For example, you can now use it to create a web-based throttle with a cab video image live, for someone to run your layout from anywhere in the world! (assuming you can master all of the technology involved, which I have yet to do!).
The bad news is that it takes a lot of overhead care and feeding just to keep all the "user files" connected to the "program files" as you and JMRI update your computers, operating systems and versions over time. A lot. I am always in a hurry to get things done, which makes things much worse, because one dumb mistake on my part and my JMRI is crashed for months.
It would be easy to say "get a spare computer, load JMRI on it, unplug it from the internet, and use it only on your railroad for the rest of your life." I know some people have done that. However, I like to keep buying locomotives and setting up their decoders consistently with the rest of my fleet, so I need to keep upgrading to the latest version of JMRI, which means keeping my computer's operating system up to date and whatever version of Java that the latest version needs. If I understood any of this, it would be one thing, but I don't.
A year ago, my beloved computer program for making car cards, "Waybills" by Shenware, which doesn't have a version for Mac iOS, crashed on my "PC emulator" that I was running on my Mac. Without going into details on the ensuing nightmare, I ended up buying both a new PC and a new Mac. Thinking that I would keep the PC in the basement with the train layout and the Mac in my office. In the end, I was only partly able to get Shenware running properly on the new PC, and the company is no longer supporting its product, so I'm not likely to ever get it fully functioning again. Very bad news. But then I turned to the idea of putting my "user files" from JMRI on Dropbox so that I could run JMRI both from the basement and from my upstairs Mac. I tried this, in a big hurry as usual, and the result was that both installations of JMRI crashed. So this left me without both my beloved car card program and Decoder Pro or any of my dispatcher panels on PanelPro or operations scenarios in OperationsPro (all very useful features of JMRI).
So I stopped having op sessions of any size and turned my time and attention to layout construction and making YouTube videos (which hopefully you are enjoying at https://Youtube.com/@muchfunwithtrains) , hoping that some day I would get JMRI working again.
Well, today it happened! I can't explain any of it, but I tried opening JMRI on my Mac and it worked! It found the latest version of Java that I had previously installed, and it was able, with a little prodding, to find my locomotive roster data. The following photo is proof. I just installed a new loco, SP&S RS-3 #90 in the JMRI for my HO layout. I haven't tried looking for the panels in PanelPro yet, and have no confidence at all that I will find them, but at least I can get back to working on locos using DecoderPro.
Just a note on Dropbox. After using it for a few years for various file transfers and such, I finally realized that I had not one, but three emails associated with Dropbox files that my computers were using. It is next to impossible to figure this out, or what to do about it. I haven't tackled that yet, but I'm only going to try sharing JMRI between my two computers after I somehow straighten that mess out. In the meantime, I'll probably just move my Mac downstairs and plug it in to the layout for operating sessions. A shame, but I don't want my hobby to become "computer technician" any more than it already has.