Hi there! I am on the staff of the Official Mocreatures Server, and we have figured out the most common issues that cause this error.
1: It's best to always download from the official site, mocreatures.org. That way the file is formatted and named correctly
2: Usually the issue comes from the jar file being named incorrectly, whether it's the custommobspawner file or the mocreatures mod itself. Make sure theres no odd dashes or underscores. For example, the names on the jar files of our most recent versions should read:
DrZharks Mocreatures Mod-12.0.5
If you still find it isn't working after that, try using the forums on mocreatures.org. Other people knowledgable about the mod are on that forum that can help you further.
I have downloaded both of these mods and they appear as such in my folder, with the one exception that spaces are replaced by pluses (but I think that's just standard). However, the problem still persists, even when I create a new world.
Does custom mob spawner conflict with something like IvToolkit?
Edit: Fixed! Turns out I did indeed have the wrong version. Going to the modpage and downloading the files from there fixed it. It still messed with OTG but I haven't encountered any issues yet. Thanks!
I try to download the newest versions of both MoCreatures and CustomMobSpawner off mocreatures.org but when I go to download either it brings me to adf.ly which shouldn't be trusted. Sorry I didn't create my own feed but this was already here and a developer was here too so I figured this was the best bet
So to cut to the jist of it, because of the way CurseForge formats it the DrZhark-Mocreatures has a + between DrZhark and mocreatures, simply changing the + to a - should fix the issue, at least that's what his own website says.