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Check you have the latest version then contact the mod author. Also read the FAQ. Do not post logs in the forum, use a file sharing site. And always post the logs/debug.log

https://github.com/Creators-of-Create/Create/issues/5318 Use the correct version of optifine (including preview versions) that matches the version of forge you are using - see their download page. Otherwise, you need to report optifne bugs to them. Also, when reporting problems in this forum, you need to post a link to the full logs/debug.log - do not post logs in the forum. See the FAQ at the top of this forum.

If you are posting compiler errors then you are in the wrong forum. This is a support forum. It is not a place to learn minecraft modding or java. We help people that have already implemented something but it doesn't work as they expected. To receive such help, you need to provide a working example (preferably on github) that reproduces your problem. Code snippets out of context in the forums do not qualify. For your specific observations. Forge changed to the Mojang deobfuscation mappings for minecraft 1.17 https://gist.github.com/50ap5ud5/beebcf056cbdd3c922cc8993689428f4#full-migration-to-mojang-mappings Trying to use the old Forge mappings from 1.16 and before, whether examples, tutorials or docs isn't going to work unless you understand how to translate them. Forge only documents the things it changes and maybe other bits that are relevant to those changes. It does not try to document the whole of Mojang's Minecraft source code. Efforts to do such things can be found in for example in the parchment project: https://parchmentmc.org/ The translations you are looking for in your particular example are: Old Forge => Mojang official World => Level onBlockPlacedBy => setPlacedBy Do not expect to be able to ask for other such mappings. You need to do your own research.