Your Thunderbolt cables don't have the lightening bolt logo on them? I didn't think it was a 'requirement' but every TB cable I've seen always has the thunderbolt icon.
https://www.apple.com/shop/product/MD862LL/A/apple-thunderbo...
Correct link: https://www.apple.com/shop/product/MQ4H2AM/A/thunderbolt-3-u...
What a mess…