I'm still dealing with my localhost, and I do different tests and it works with 2CO, until I use it with https and it's still working.
in order to reproduce the issues, you can try here
http://lakompra.us/osclasspay/itempaypub/40/1.
I set up paypal and payza and is working but is not available in my country, just can use 2CO.
Once again in localhost is working, under the sandbox account I have all the localhost transactions, the only difference is because localhost is using PHP Version 5.6.28 and my lakompra.us is using
http://lakompra.us/phpinfo.php PHP Version 7.0.23. but like I said paypal and payza is working.
Checking this information
https://www.2checkout.com/documentation/payment-api/create-token, said that is Request failed. Payment API error.
** additional I cannot sent the emails from this plugin, and is not working including in my localhost, all the others emails works,
I try disable, paypal and payza in order to avoid conflicting, but still having the same error. Please check the attachment, I try with live account and sandbox.
Thank you for your time