A participant hasn’t received the invitation, how can I resend one?

That is unfortunate. There could be a few different reasons for that. To narrow down, the cause:

• Verify that the email is correct. In My Workspace > Contacts > View details (eye), you’ll be able to see the email address. If incorrect, delete and re-invite.
• Verify that the right contact was invited to the activity
• Ask the person to check filters (e.g. junk mail or spam filters)

You can try to re-invite the person. Contact Customer support when you need help.