I am trying to use a schematic in a multiplayer world and it is not loading the blocks in a visible manner. I get the schematic area box as well as a shadow on the ground showing that the blocks are rendered in but there are no placement blocks visible. In my private world I can use this just fine everything works normally. Other people on the server are saying it is working just fine. I went through all of my settings to try and fix this and nothing is working. It has to be client side but I can't figure out where it is. I have reloaded everything multiple times including all of Minecraft as well as all the schematics. I even made a new schematic in that world and it still doesn't show the blocks for that schematic. No one seems to have seen this issue before. If you have a fix I would love to hear it but I don't know how you'll be able to recreate this since it seems to be unique to literally me.

as well as a shadow on the ground

This means that you are using shaders with the Iris mod? Shaders currently break the schematic rendering. The Iris mod developer has been working on some things to try to fix this lately, so hopefully it will start working at some point.

For now you will need to disable shaders and then toggle off and on the schematic rendering to refresh it and make it render.