Tcpreplay has a mailing list for it’s users. However, before posting a question, please read the short README included with the latest source. It explains what information is needed to answer many tcpreplay related questions. You’d be amazed how many people don’t even say which version of Tcpreplay they are using!
There is also a mailing list for people interested in Tcpreplay development.
If you are reporting a bug please submit it on GitHub Issues.