Soapbox Engage requires the value "Closed - Converted" for Lead conversions to happen as part of our triggers that automate the Lead conversion process. You can customize the Lead Process values to include additional options, but "Closed - Converted" must remain included in order for our triggers to fire, otherwise you will likely see this message:
Apex trigger sbxd.sbx_DonationsCampaignMember caused an unexpected exception, contact your administrator: sbxd.sbx_DonationsCampaignMember: execution of AfterInsert caused by: System.DmlException: ConvertLead failed. First exception on row 0; first error: INVALID_STATUS, invalid convertedStatus: Closed - Converted: : (sbxd)
If you are seeing this message, no worries! It just means you need to add the "Closed - Converted" status back to your Soapbox Donations / Submit / Registration lead processes as an option.
To do this, go to Setup > Customize > Leads > Fields and confirm that "Closed - Converted" is included in the list of existing picklist values. If it's not there, go ahead and add it.
Then go to Setup > Customize > Leads > Lead Processes and make sure the "Closed - Converted" option is assigned for each Soapbox Engage process (Soapbox Donation, Soapbox Registration, Soapbox Submit, etc).
Then you should be all set and can try your test to make sure lead conversion is working properly.