Under Payment Gateways, my primary gateway is Authorize.net.  Further down in Payment Gateway Setup, I have Show PayPal Checkout Option selected.  My question is - will the IPN process work when using PayPal in this "secondary" way rather than as the main gateway?

Using DNN 7.2.0 and SmithCart 5.68.0. I thought I had everything set up right, but had a user check out with PayPal on Thursday and had a Module Load Exception in the log:

ModuleId:568
ModuleDefId:146
FriendlyName:
ModuleControlSource:DesktopModules/Smith.BuyNow/IPN.ascx
AssemblyVersion:7.2.0
PortalID:0
PortalName:XXXXX
UserID:-1
UserName:
ActiveTabID:147
ActiveTabName:AAD Store
RawURL:/aadstore/tabid/147/ctl/ipn/mid/568/default.aspx
AbsoluteURL:/Default.aspx
AbsoluteURLReferrer:
UserAgent:Mozilla/5.0 (Windows NT 6.1; WOW64; rv:5.0) Gecko/20100101 Firefox/5.0
DefaultDataProvider:DotNetNuke.Data.SqlDataProvider, DotNetNuke
ExceptionGUID:GUID#HERE
InnerException:The method or operation is not implemented.
FileName:
FileLineNumber:0
FileColumnNumber:0
Method:Smith.Modules.Gateway.SmithHostedIPNGateway.Create
StackTrace:
Message:
DotNetNuke.Services.Exceptions.ModuleLoadException: The method or operation is not implemented. ---> System.NotImplementedException: The method or operation is not implemented.
at Smith.Modules.Gateway.SmithHostedIPNGateway.Create(String gatewayCode)
at Smith.DNN.Modules.BuyNow.IPN.Page_Load(Object sender, EventArgs e)
--- End of inner exception stack trace ---
Source:

It actually seems the IPN may have worked because the Payment shows APPROVED in the store, but no emails were sent from SmithCart - something I had attributed to PayPal not confirming payment.