Error Uploading .CSV

I'm trying to upload a CSV, but I keep getting this error:

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File check complete

Error: The server encountered a problem trying to import your file. Please check that it is a plaintext csv file and try again.
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I've uploaded a whole bunch of CSVs tonight without issue (I'm inputting a large collection piecemeal), but I just started getting this error. Can someone please post a fix, or check out my account and see what's wrong? Thank you!