When MODX is installed in a subdirectory the URL duplicates the subdirectory part:
otpauth://totp/admin::http://localhost/revo231//revo231/working/?secret=H5BOBZZ2F7PUJ5RI&issuer=Revo+2.3.1+Local...
Note the extra /revo231/ in there. I had my "manager" folder renamed to "working" in this installation.