Hello and welcome to the community. 
Here are some things for you to try:
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Check your quarantine menu (sometimes also called the virus chest) in your antivirus program to see if a WeMod file is stuck in there, if there is, de-quarantine it. There have been cases of files getting stuck in antivirus quarantines despite exceptions being added.
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Make sure you have the latest and uncorrupted version of .NET Framework. Even if your PC says you already have it, re-install it anyway: Microsoft .NET Framework 4.8 offline installer for Windows.
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Make sure the file path to the game’s .exe in WeMod is correct. To do this, click the downwards arrow next to the Play button and manually link the .exe there. By default, the game else is in
C\Program Files (x86)\Steam\steamapps\common\GAME_NAME
If you’re still not sure where the correct .exe is, see the “Custom Path” header in this thread: "Wemod failed loading the cheats into your game" / "We’re having trouble downloading the cheats" - #2 by Ravenfyre.
Do not use any shortcuts (ie, on your desktop) to link WeMod to the game, these shortcuts are the launcher, not the game .exe. -
Make sure you are using the most recent trainer version by clicking the History button in the trainer and selecting the most recent one in the list.
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Uninstall and re-install Steam.
If you’re still having issues, please use the trainer until it fails, then go into your WeMod settings by clicking the cog wheel in the top-right and download the log, then share it here.