Sand cannot be put into any sieves besides tier 1 string one, and does not drop anything even after hundreds of sand inputs. It is stopping my ex nihilo skyblock survival. I cannot get any drops from it so I cannot get ancient spores.

Are there any recipes using sand visible in JEI please upload your SieveRegistry.json file to pastebin and post a link here.

what is JEI and how do i find SieveRegistry.json?

JEI is a mod which lets you view recipes, creatio has support for it and it can be used to see what items drop from what blocks+meshes. SieveRegistry.json would be in /configs/exnihilocreatio and if enabled in /configs/exnihilocreatio/exnihilocreatio.cfg is used to customize the drops that different block+mesh combinations give.

When you have more information please open a new issue.