When you get zip folder downloaded, unzip it the contents into the obs studio root folder under program files. Make sure its in the correct folder. Make sure you do not have obs running and make sure you keep obs to run as administrator or some features just wont work.
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If it asks to overwrite anything, let it.
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After you xfer the files to the obs folder it should look like this
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hope this helps. if you ever used the old obs and never uninstalled it, there's a good chance you may have put it in the wrong folder. If youre still using classic then I recommend you upgrade to studio as I don't think much of anything works in classic anymore.