The Federal Election Commission in a letter dated June 2nd, questions contributions received by Carr's campaign. It says, "Schedule A of your report discloses a receipt/contribution without an explanation that appears to be from a limited liability corporation" Also, the letter notes that, "Schedule A of your report discloses one or more contributions that appear to exceed the limits set forth in the Act."
To see the letter, follow this link. Admittedly, campaign finance can get complicated and that is why serious campaigns hire professional campaign managers and appoint competent treasurers to help with that sort of thing. Joe Carr is not very good at all of that paper work stuff.
To see who contributed to any federal campaign and how much they contributed you can find that information at the Federal Election Commission's website. Here is the link to Carr's report.