The startup script refused a setting before downloading anything

Your log will have other names, versions and times. Search a line of it from all failures.

What it means

At startup, the server’s Docker image runs a helper tool that installs the server software and any mods or plugins you listed. Before it fetches anything, the helper checks what each command was given. One of those values did not make sense to it, so it refused, and the server stopped before it started.

The issue carries the helper’s own sentence, which says what it refused. A Minecraft version the software does not offer is a separate issue (version_not_available); this one covers every other refusal.

Why it happens

A project that does not exist on Modrinth, often a typing mistake in its slug or ID.
A project with no file for this server: a mod listed on a plugin server (or the other way round), or a project that has no version for the server’s Minecraft version yet.
A pinned version that does not exist for that project.
Another value the helper cannot use, as its sentence says.

How to fix

Read the sentence the issue carries: it names the project, version or value that was refused.
Look the project up on modrinth.com and check its slug, its type (mod or plugin), its loaders and the Minecraft versions it supports.
Remove the project, correct its name, or pin a version that exists for this server, then start the server again.
If the project has no build for your Minecraft version, wait for one or leave it out.

In Perland

The issue appears in the server’s Diagnosis tab with the helper’s sentence. Correct the setting it names (a project, a version, an address) in Settings, then start the server again.

References

Details the diagnosis reports

Perland's server diagnosis returns this failure as the code startup_invalid_parameter with these parameters, each present only when the log names it.

Parameter	Meaning
`command`	The startup helper's command that refused the setting, such as modrinth.
`detail`	The helper's own sentence saying what was wrong, such as a project it could not find.

Log lines this page covers

Invalid parameter provided for 'modrinth' command:
Project(s) could not be located:
No files are available for the project
does not have any matching versions for loader