No errors displayed when invitation email failed

[tianrunhe]

Issue - Bug

Reproduction step:

1. Create a new team
2. Send 10+ invitation emails
3. Immediately try to send another 10+ emails
4. See no emails were sent for the second batch, but there is no error either

Acceptance Criteria (optional)

Users can:

• Receives proper error if team invitation emails failed for any reason, e.g., "you have sent too many emails recently", or "wait for your last 10 invites to accept before sending more"

Triage is performed to find the root cause of the bug, timeboxed to ~1 hour.

Estimated effort: 1 hour to triage. More if root cause is already identified.