Select at least one permission
The product refuses a save where neither download nor upload is selected. Full text: “Select at least one permission (download and/or upload).”
Why this happens
Same idea as Download or upload must stay enabled: a context that needs at least one of those actions cannot be saved with both off. The string lives in the error catalog; if you see it (or a related validation), treat it as a both-off permission save.
Diagnose and fix
1. Turn on download, upload, or both — then save again.
2. For plan tiers: Admin → Settings → Users & limits — toggle.ul2_upl_on_* (uploads) and toggle.ul2_dnl_on_* (downloads). Leave at least one on.
3. Check per-user overrides if only one account fails.
4. Re-try the action that returned the error.