Thanks Leo,
My dispatcher.php file already has the line shown as added in the link you sent (line 36). I'm on 1.7.7.0.
Here's what it looks like:
// Cart is needed for some requests
Context::getContext()->cart = new Cart();
Context::getContext()->container = ContainerBuilder::getContainer('webservice', _PS_MODE_DEV_);
Context::getContext()->currency = Context::getContext()->currency ?? new Currency(Configuration::get('PS_CURRENCY_DEFAULT'));
Andrew
.png.022b5452a8f28f552bc9430097a16da2.png)