Many Knock connectivity issues are related to Bluetooth interference. Most of these issues arise from Bluetooth storing improper identifier values. In order words, sometimes Bluetooth will mistake known devices for new devices and cause errors. Often, checking your Bluetooth settings and clearing the Bluetooth cache can help resolve this type of issues.
On your Mac, go to System Preferences > Bluetooth, remove any devices you no longer use. On your iPhone, go to Settings > Bluetooth, remove any devices you no longer use. If your Mac and iPhone are paired, unpair them.
The Bluetooth cache is managed by the Blued process and helps reconnect to known devices faster. Sometimes Blued may store a corrupt value and cause Bluetooth to mistake known devices for new devices and cause errors.
Clear the Bluetooth cache:
On your iPhone
1. Reboot device: please hold the sleep button for a few seconds until you can power off.
2. Turn device on and open Knock app
On your Mac
1. Quit Knock if it is open
2. Turn Bluetooth OFF
3. Delete file named com.apple.Bluetooth.plist from /Library/Preferences. (If you can’t find the Library folder, go to Finder and select the Go menu, hold down Option key and Library will display)
4. Delete file named com.apple.Bluetooth.plist from /Library/Preferences/SystemConfiguration
5. Delete file named com.apple.Bluetooth.somerandomcharacters.plist from ~/Library/Preferences/ByHost (note that this is the user preference folder, not the system one)
6. Delete file named com.apple.Bluetooth.plist from ~/Library/Preferences/ByHost (note that this is the user preference folder, not the system one)
(the full file paths looks something like this:
6. Restart Mac
7. Turn Bluetooth ON
8. Open Knock
Open Knock once more under these conditions.
If Knock continues to experience issues, relink Knock.
1. on the iPhone, open the Knock app and drag the computer image down to the X
2. on the Mac, click on the Knock icon > unlink > you may force unlink > quit Knock.
3. Restart Mac and relink