When I see this "EPG Update complete. [0 inserted, 0 updated, 238 skipped]" it seems that
1) the source is not very complete, typically PVR will have more than 238 shows but it shows that the guide is being updated.
2) your XMLTV file is stale. Typically this happens when you point to a local file that you aren't updating correctly. If it is online your source is probably just bad. It could also mean that the guide data matches the m3u file.
Feel free to post your zipped NextPVR logs on the NextPVR forum and we can have a look.