Installing or updating mods in this game is weirdly unstable to the point I'm making this post. I think I should've done it far sooner.
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First a tutorial on installing mods in From the Depths. Most new players don't realize it requires two-three steps:
-Subscribe to the mod on Steam
-Boot the game and on the main menu press "Download" then select the mod you subscribed to and then press "Save mod in..."
-Reboot the game and you should now have the mod installed and visible
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If the installation/update fails:

-Go to "C:\Users\'Your User name'\Documents\From The Depths\Mods" and delete the "MoreSimpleWeapons" mod folder
-Repeat the installation procedure of the installation tutorial above

If everything fails:
Download my mod folder from the link and put it in the "Mods" folder in "C:\Users\'Your User name'\Documents\From The Depths\Mods"
Remove the space in "https" for the link to work:

h ttps:/www.mediafire.com/file/bfd7gnzak4gsr26/MoreSimpleWeapons.zip/file