r2modman not opening: installer, permission, and sandbox checks

Record the failure before changing it

Write down the operating system, r2modman version, game build, active profile, and last known change. Capture the first meaningful error from the manager or loader log. Later lines often describe the consequence of the first failure, not its cause.

Check the highest-value evidence first

Follow this order and change only one variable between launches.

• Start from a terminal or command prompt to preserve the first error.
• Confirm the platform package, exact version, file size, and SHA-512.
• Check whether security software quarantined an application file.
• On Linux, separate execute permission, missing libraries, and Electron sandbox errors.

Create a five-minute minimal reproduction

Clone or create a profile containing only the community-required loader and one target mod. Confirm the game path, then use Start modded. If this works, restore packages in batches; if it fails, the cause is now bounded to the manager, path, loader, platform, or one package.

Avoid fixes that destroy evidence

Do not simultaneously reinstall the game, clear every cache, change Proton, delete profiles, and update all mods. Those actions can appear productive while making the original cause impossible to identify. Back up first and prefer reversible tests such as disabling a package or switching profiles.

Escalate with a useful report

When the path, permissions, loader, and minimal profile have been verified, collect the smallest reproducible profile, exact versions, first error, and steps. Remove usernames, tokens, and private paths before sharing. A focused report is more useful to project or mod maintainers than a screenshot of a generic exit code.

Verify the repair

A repair should survive two launches, a profile switch, and a vanilla comparison. Record the successful versions and what changed. If multiplayer is involved, repeat the check with one client before bringing the full group back.