Hey everyone, Shuji at Zwift HQ here.
The common thread here is that you all upgraded your iPhones to iOS18 recently. Apple OS updates (the major version updates anyway) reset app permissions to the default (more restrictive) settings, and you may need to re-allow the Companion app to use the WiFi and Bluetooth radios.
Please see this Apple support page and allow Zwift Companion to use Location Services. WiFi and Bluetooth perrmissions are bundled under Location Services, and those are what matter to Companion users. Zwift does not use GPS services in case you’re wondering.
You should notice that permissions are denied after the update to iOS18 - please let us know that allowing permissions solves this issue?