Openinv Version: 4.1.8
Paper Version: 1.17.1 Build 386

The player name is not displayed at /openender name.

All right, thanks for the information. Have a great day.

This was fixed a while ago. Unfortunately, as the language key did not change, you will need to manually fix it in your en_us.yml - the string should have been %player% but it was %Player. Alternately, if you have not modified it, you can safely delete it and let it regenerate.