NVMe Samsung 960 evo (with adapter) + MBA mid 2013
As long as you know that the hardware you specified is indeed compatible with your make/model of MacBook I would first look into everything being installed properly. Make sure everything is seated correctly and there is nothing that does not belong.

You may also want to take the replacement/adapter out and inspect the area around where it is installed for foreign matter (dirt) use some canned air to clean out the system and parts. Inspect for damage (use a magnifying glass!).

Reinstall everything carefully and see if it is any better.

If the same symptoms persist you are faced with possibly replacing (under warranty, hopefully) the SSD and/or the adapter. Contact the reseller and see what they say. They may just take both back. I would be inclined to do just that as there is no way of telling which part is defective.