This is like you telling us your door won't close, but not saying anything else and not letting us see the door. We have no idea what's going on. I assume you have shaders enabled in the shaders area? Are they compatible? If there is red text in the corner you've selected a shader that doesn't work with Blockland and the compile failed. Try disabling all shaders and re-enabling them one-by-one until it stops working, and whichever you enabled latest you can't use. Skip it and start enabling them again, repeat until all wanted shaders are enabled or incompatible.
If there's no text in the corner at all when it starts, you've got bigger problems.