Steps
Verify you have Admin or Owner permissions (check your role)
Ensure you're inviting with the correct email address
Check that the person isn't already a member of the workspace
Verify the email address is spelled correctly and valid
If inviting multiple people, try inviting one at a time
Clear your browser cache and try again
Try a different browser or incognito window
Contact support if you still can't invite after these steps
Notes
Only Admins and Owners can invite workspace members
Each email address can only be invited once
Invalid email addresses will be rejected
Invited members must accept within 7 days