Think it has to be done in the same manner as Ark's official spawn codes, which include the name of the dino twice at the end, instead of just once, with a full stop (period) between:

/Deinosuchus_Character_BP.Deinosuchus_Character_BP

Also you might have to define the mod's directory with it's mod ID number, but I'm not sure on that one.

Okay I'll try that, thank you so much for giving me some good idea's or pointers. I am desperate to be Deinosuchus!

So the files are looking like this.
/Ark/ShooterGame/Content/Mods/1130324993/Dino/
And then I can see the Deinosuchus_Character_BP file. Not sure if this helps clarify anything that might help, but I don't see it in the order that the other guy said. I don't see any /Game/ file or anything, unless /ShooterGame/ is /Game/?

It didn't work...

Yeah, the official spawn commands substitute just 'Game' for shootergame and don't have the /Content section. So try deleting those two.

/Game/Mods/1130324993/Dino/Deinosuchus_Character_BP.Deinosuchus_Character_BP

If that doesn't work, look on the mod page of the deino to find it's admin spawn command (if the mod page doesn't list it, ask the mod author for it). Then when you get it, delete the bits from it that you don't need and just keep the bits you do.

To use an official creature spawn command as an example:

admincheat SpawnDino "Blueprint'/Game/PrimalEarth/Dinos/Raptor/Raptor_Character_BP.Raptor_Character_BP'" 500 0 0 35

Delete this: admincheat SpawnDino "Blueprint'

And this: '" 500 0 0 35

So you're just left with:

/Game/PrimalEarth/Dinos/Raptor/Raptor_Character_BP.Raptor_Character_BP

Do that for the mod dino spawn command, and paste it into the custom dino box.

Okay I'm assuming the code you gave me worked because it now says "You are not allowed to play as a Custom Dino" instead of the common Invalid Class line I was getting before. How do I set up custom dino's on my server?

That one is an .ini config setting for the mod. Check the configuration topic for info on that ;)

https://psteamcommunity.yuanyoumao.com/workshop/filedetails/discussion/520154171/357287304416622429/

Okay so I did everything and got it to the customization screen, but now everytime I complete and spawn nothing appears. I just spawn in as a invisible human.
How do I fix this?

I think that's just a glitch with the mod, I get it from time to time. Try pressing ESC and selecting to change dino, then respawn...that usually fixes it. Or if it doesn't change dino and create a random throwaway animal, spawn in with that, then change dino again and remake the deino character.

It still hasn't been working, I've done everything. It only lets me spawn in as Deinosuchus (Custom Colored) in Single Player. On my server, it should be no different, but it for some reason still doesn't allow it. I have to manually spawn, force tame, and then hopefully I get the right gender and colors.