Hmm...
Options:
1. Re-download ZAPT.
2. An add-on might not be compating well with ZAPT (this can happen even you have only the default add-ons + ZAPT enabled on your server), try putting all of your add-ons into another folder except ZAPT, then launch Blockland. If it works, then an add-on is not compating with it, if it doesn't work, then try another option.
3. Re-install Blockland.