Try removing the client add-on named "Overhaul_NovaPack". It has an error when it loads. If Blockland still crashes after that, I recommend re-installing Blockland.
That's actually an April Fools' prank mod. Remove it. No need to reinstall, and it probably won't help. I almost never recommend that to people.
OP, rename your add-ons folder to "Add-ons Old". Then try again and report if it works.