Version 1.40 introduced significant changes under the hood (especially the new lighting system and how models are rendered), which broke many older mods.
Version 1.40 requires updated map assets. Pirated clients often fail to load complex map expansions like ProMods due to incomplete file verification. Ets2 1.40.4.8 Product Key
For a version as specific as 1.40.4.8, finding the associated key is often the biggest hurdle. Here is where to look based on how you originally purchased the game: Version 1