I'm using Person Accounts with Actions but Salesforce creates new Contacts as Business accounts

One thing you can can check is that as indicated this documentation from Salesforce:

Salesforce provides one default person account record type, PersonAccount, but an administrator can create additional person account record types.

The Soapbox Actions for Salesforce app assumes that this is the case.

The problem may be that the name of that record type has been changed in your account. For example, instead of "PersonAccount", it might "Person_Account" or "Person Account" or something entirely unique to your org.

If you look at the Record Type Name in the Person Accounts record type, you may see that.

Return the record types name to "PersonAccount" and this issue should be resolved.