Units are not spawning

[King David]

No units in sand box mod are spawning for me. Anyone else dealing with this?

[javelin7]

I am

[Boanz]

I've been having this issue. At least I'm assuming we are having similar problems.

This is how I fixed it.

In my case, I would try to build a scenario in the sandbox editor. I would start with two army groups as usual, and then of course end up adding more different units, modded or custom etc.
Eventually, one of the groups just would not appear, and the other groups would just sit there. Well here's what I did to work around this...
1. Go back to the sandbox editor part, and click on the Reset All button that is down in the bottom center. This will delete the army groups down to one or two groups. You may have to click it two or three times. Don't worry, this is so you can kind of start over, and it only takes a few moments to add the groups back in. But first, test the scenario without adding anything extra beyond what was there after hitting the Reset All thing. (And by this I mean you will need two armies, a team 1 and a team 2) Set all the units to Attack, instead of Hold or Guard.
If the scenario seems normal, all units appear and they start moving out on the attack, it's normal. Go ahead and exit back to editor.
2. Now, SAVE the scenario, since it was working.
3. Now you can try adding a group. Doesn't matter which team (at least I don't think it does), but I try to keep them in order if possible. But my latest scenario does not have them in team number order, and the scenario is working.
4. After adding a new group in, test it out. As above, if they appear and begin moving on the attack, it's normal. Exit out and save again.
5. If the units do NOT appear, and / or other units do not move, then something is wrong with that new unit you just added. Exit out, and DO NOT save, but instead, RELOAD the scenario back to the last time you saved it, when it was working.
If you are trying to add a custom or modded unit that you really want to have in the scenario, but it is just not working, look through the Unit Category lists on the left, OR click on Character Customization in the lower right to make sure you have it present in both the normal / modded category, AND in the Custom category. (Custom is units you have edited or created yourself). Yes, you may need to edit it and therefore make a Custom version of it. Even if you do not change any of it's stats, but you will want to give it a slightly different name.
For example, the Apache helicopter; In the modded category it would appear as Apache in the drop down list. So, what I do is simply add a "II" behind it's name, therefore I have in my Custom list Apache II.
If you find that you have the Custom version of the unit, (Like the Apache II) but it seems missing in all the other categories, (no Apache in Modded, WW2, Roman TImes, Ancient Greece, etc) then somehow it got deleted. This could be messing up your game right there. I mean, I don't know, but it could be that the game still has to look at the original file data to create the unit in your scenario, even though you still have, and are trying to use, the Custom version you made.
What I did when that happened was, I uninstalled the game from Steam. Then, I did a file search in file explorer, and found a folder in C:> Users > (your name) > AppData > LocalLow > Brilliant Game Studios. I simply deleted that entire folder. THEN, go back to Steam and to your Library, then Install UEBS 2 again. The unit *should* be back. You may have to go to the workshop (if you got it there to begin with), and then Unsubscribe from each one, and re-Subscribe to each one, to make sure they are downloaded into your computer. THEN, they should appear again in the appropriate drop down list.

Anyway, I hope my experiences can help someone out there. This game is astonishingly good, it just takes a bit of patience sometimes to get a battle scenario to work right. I mean, despite all this, I still don't know why it is that sometimes units just refuse to spawn in. Sometimes they just don't. Maybe it has something to do with Steam storing your data in the "cloud" instead of actually having it stored locally on your hard drive (which is a HUGE mistake IMO). Hopefully the devs will keep working at it, and smooth out these glitches.
Good luck, and don't give up!