Paypal Check Error

I just installed Sytist and everything seems to be working fine except the Paypal Checkout feature.  In both the sandbox and live versions, I get "Error: Unexpected token" while the transaction is processing.  It looks like the transaction actually went through (from a financial perspective) but did not show up in my orders on Sytist.

Paypal Standard Business worked correctly though.

I tried on both desktop and mobile in browsers not related to the setup of Sytist.  

I double check and SSL appears to be set up correctly, and I modified htaccess per the instructions elsewhere.  

My hosting is on KnownHost.

thanks!

That can happen when using live credentials in sandbox mode and vise versa. 

There will be a recent errors section. See if there is anything under that and if so email me what it is.

Thanks Tim.

Nothing in recent errors in Paypal.  Confirmed I was using live credentials on both Paypal side and Sytist side.  Only info I have is the dialog box in the picture above.  Just planning to use Paypal Standard right now since that seems to be pretty bullet proof.  I'm switching over from Zenfolio and orders are coming in, so I may revisit once pre-orders die down.  THanks!