Login to your TWINT dashboard using this link.

Press on "Stores" on the left side menu.

In the online shop section (1.) please select the "edit" button (2.).

In the "further details" section (1.) please select the "edit" button (2.).

In the "Integration" section, please make sure that you have selected "Shop plugin" (1) and select "Shopify Plugin by TFTW" (2) for Shopify or "WiX Plugin by TFTW" (2) for WiX from the dropdown. Now please click on "Next".

Shopify:

WiX:

Please click the "Save" button.