Only use original saves that have never been used with mods.
To clarify: - The forum where we are now is for 32bit Skyrim / Skyrim LE.
#SKYRIM SPECIAL EDITION NO ACHIEVEMENTS MOD#
That version does disable achievements from any mod plugin, if you are not using files from Nexus to disable that behaviour. Simply copy your old saves from My Games/Skyrim to My Games/Skyrim Special Edition. Skyrim Special Edition is 64bit version of the game, which is sold as separate game in Steam.
#SKYRIM SPECIAL EDITION NO ACHIEVEMENTS PATCH#