PayPal Checkout Problem

[Acmiron]

PayPal Express Checkout in Production displays a Blue Wheel.
Like the wheels on a bus, the Blue Wheel is turning round and round, always round.

After a very long time, "500 Internal Server Error" is displayed.
No matter which changes are made in the VM PayPal configuration, the error remains.
Also disabling SSL in VM has no influence.

I have cleared cache, history and stopped InterNet Security: same result.
I have used another browser: same result.

Sandbox functions!

Joomla 3.9.5, PHP 7.2.17 and VM 3.4.2 with the VM plugin for digital goods.

What is the difference between Sandbox and Production in VM?
Must I declare something somewhere in VM configuration (Shop, Product,  or ... ) for digital goods

Please advice

[Jörgen]

You should use ssl, turn on in joomla configuration or htaccess.
Is this in sandbox mode? You have to turn on sandbox in paypal plugin configuration. Have you set up sandbox accounts with paypal ?
Have you tried standard template? Protostar or beez ?

Jörgen @ Kreativ Fotografi