When you're trying to manually convert a Lead that has the "Soapbox Registration" record type, you might find that you receive the following error message.
There was an error converting the lead. Please resolve the following error and try again: sbxe1.sbx_EventsLead: execution of AfterUpdate caused by System.QueryException: List has no rows for assignment to SObject Trigger.sbxe1.sbx_EventsLead: line 57, column 1
This likely means that when you tried to convert the Lead with Salesforce, the checkbox for "Don't create an Opportunity upon conversion" was checked. Soapbox Events for Salesforce package needs to create an Opportunity record for it to complete its processes successfully.
On the lead conversion screen within Salesforce, make sure that the "Don't create an Opportunity upon conversion" is unchecked before you convert the Lead.