Why isn't my Facebook pixel showing 'initiate checkout' on Shopify?

Hi, I have my facebook pixel installed on my shopify website. Although the event ‘initiate checkout’ appears as active in the Overview tab of Events Manager, when I do a test in the events manager, ‘initiate checkout’ does not show:

And also it’s not showing in the Chrome Pixel Helper:

I wonder if this is related to the fact that the URL I see when I initiate checkout, is not with the standard words, like checkout/processing or checkout/payment, but rather a long series of numbers and in between the word ‘checkouts’ in plural:

If you think this is the problem, could you please tell me how I can change the URL, so that it appears, with the common set of words (checkout/processing or checkout/payment, /checkout/shipping), like it does in the case of the ‘added to cart’:

If not, any suggestions on how I can solve this?

Any help would be greatly appreciated!