What version of OBS are you using? You mention “the big 26”. Does that mean Version 26.0?
The Off-World-Live plugin release 1.9.0 says " built against OBS 31.0.X". I have tested the direct extraction to “C:\ProgramData\obs-studio\plugins” with OBS version 32.1.2 and it works OK.
I un-installed 32.2.1 and installed Version 26.0-rc3 and after extracting again to “C:\ProgramData\obs-studio\plugins”, the Spout2 plugin does not show in OBS.
I then un-installed 26.0-rc3, re-installed 32.1.2, and extracted the plugin file. After that it shows up again in OBS.
If you are using OBS in portable mode, there is another method to use.