Thanks for attempting yourself and seeing my problem. I finally figured it out, thanks to your help! I had to completely copy/paste and resave the originally used file in a different document. Then close and reopen ArcMap, join the table and it worked. I just want to note some things for people who may have a similar issue. I had re-save the original file used in the first join, and I couldn't fill in the 'bad' columns with an additional join. For example, I had one column at one point that was all null values, and trying to delete that column and joining a separate .csv with only that column did not work. I HAD to close ArcMAP and reopen, otherwise several columns gave me all null values. I had to re-add the data from ArcCatalog, and I couldn't use the saved .mxd file that I originally was using. Thanks again!
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