Your case is not designed for the custom blade SSD’s Apple uses, its designed to support a 2.5” SATA drive.
Your MacBook Pro uses a PCIe 2.0 interface using two lanes (x2). You can find out more here: [https://beetstech.com/blog/apple-proprietary-ssd-ultimate-guide-to-specs-and-upgrades#hdr-15|The Ultimate Guide to Apple’s Proprietary SSDs - Generation 3]. Here’s another good reference:
[image|1494140]
Here we can see the Orange PCIe/AHCI path uses a different interface than the Red SATA/AHCI pathway.
So the external case needs to have the ability to convert the PCIe/AHCI connection to USB3. I’ve been using the OWC cases (I have four different ones now!) While a bit expensive you can often find them for sale on eBay but you need to make sure you get the right one.
Another source other than OWC which I have not checked out is this one: [https://www.ebay.com/itm/QNINE-USB-3-0-PCIe-SSD-Enclosure-for-2013-2014-2015-2016-Macbook-Air-Pro-Retina-/253297055809?nma=true&si=p6y7oZpnaWQRTgBpiQ%252Bk4zBjXRs%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557|QNINE - USB3.0 PCIe SSD Enclosure - $116.71 US] Which for some reason is more expensive then the [https://eshop.macsales.com/item/OWC/MAU3ENPRPCI/|OWC - Envoy Pro - $95.75 US]