Ensure you disable all other mods except ours before playing. If the mod does not load at all, follow this guide:

HOW TO RESET THE PARADOX MOD LAUNCHER: Go to Documents/Paradox Interactive/Stellaris, delete launcher_v2.sqlite, go into the mod folder, delete all of the ugc files, then verify the game cache in Steam and rebuild your mod load order.

If the above steps do not work, back up your custom races and personal mods and delete the entire Documents/Paradox Interactive/Stellaris folder and then verify the game cache in Steam and rebuild your mod load order again.