I am sorry to hear this has happened. Can you help with some additional information in order to troubleshoot this?
- What browser/version are you working in? I would like to try to replicate the situation on my end.
- Are you adding contacts in to the “Enter Contact details” box or into the “Paste names & Emails” box?
If you are adding contact details, what information were you adding? IE, all five fields?
- How many contacts (estimate) do you think you were adding?
- Did you see any error message about the page timing out?