Check / remove proxies from iPhone USB Personal Hotspot

This one drove me nuts but I believe this will work for most of you:

Basically the APN settings for the Hotspot were missing.

If you can browse the internet on your phone and you can activate your Hotspot but you get the yellow exclamation mark on the computer's wifi or the 'Network cable unplugged" with USB tethering, try the following:

1. Open Settings -> Mobile Data -> Mobile Data Network
2. Check the APN/Username/Password settings under "Mobile Data" (most of the time username and password - if used - are identical, if not search APN settings on your provider's homepage)
3. Enter the same settings under "Personal Hotspot" further down on the same settings page
4. Return to Settings Menu
5. Switch Mobile Hotspot off and on
6. Connect to your Hotspot -> Internet on your computer should be working now

The problem appeared for me while roaming/after changing sims, basically every time the network settings get reconfigured and the APN settings automatically change for the roaming network/new network.

Hope it works for you too!

Client isolation. It is your enemy and your friend here. This makes it so not only can you not access your iPhone from your MacBook, but other devices on the network cannot access your MacBook or your iPhone either. There are a number of ways to implement client isolation on an IEEE 802.3 (Ethernet) network and even more ways on a IEEE 802.11 (Wi-Fi) network, but they all essentially accomplish the same task - clients are only allowed to communicate with the access point and/or gateway.