thunderbolt ports not working

walcolm wrote:

why does the thunderbolt 4 ports stop working..what is going on?

You do not say what exact Mac is this?

old issue, new issue, what changed...

Have you tried rebooting?

Have you tried a different cable and compare your results?

Is your software up to date—Keep your Mac up to date - Apple Support

https://support.apple.com/guide/mac-help/get-macos-updates-mchlpx1065/mac

on the intel Mac —you can try resetting NVRAM/PRAM Reset NVRAM or PRAM on your Mac - Apple Support

(get at least two-three rounds of the chimes when holding the NRAM Reset)

on the M1 Mac—try SafeBoot How to use safe mode on your Mac - Apple Support to sort anomalies.

Hi,

Try to check your Thunderbolt4 ports with Apple Diagnostics if it's caused by hardware related issue(NDT001 to NDT006).

Use Apple Diagnostics to test your Mac - Apple Support

If it doesn't help, contact Apple Support or take your MacBook Pro to Genius Bar which is required to make reservation or your local Apple Authorized Service Provider to be examined your MacBook Pro there.

Official Apple Support

Genius Bar Reservation and Apple Support Options - Apple

Apple - Find Locations - Location Selector