Startup crash
Read the first meaningful error in the log and look for version, dependency, or loader references. Do not assume the final line identifies the root cause.
Missing or disabled features
Confirm the installed build and configuration. Features can differ by version, optional module, world settings, or project identity.
Dependency conflict
Remove duplicate libraries and verify required versions. Test without unrelated mods to determine whether the issue is a conflict or the base package itself.
Configuration problems
If a major update changed settings, compare the new defaults with your old configuration. Preserve the original before resetting any file.
Practical next step
Return to the compatibility section to compare ecosystems, or review the Download section before opening the supplied archive.