Bluetooth LE can be quite finicky in certain environments. Things like nearby 2.4GHz radios, other Apps that use Bluetooth, and the iPhone state impact Bluetooth connectivity.
Further, when your Mac wakes from full system sleep, it has to run an in-order wake up protocol before Knock is allowed to connect.
One of the first things your Mac does when waking is to connect to other Bluetooth devices. So, if you are paired with Bluetooth devices you rarely use, unpairing them through System Preferences > Bluetooth may help.
If you wake your Mac from full system sleep, Knock will take longer to connect. If you wake your Mac from Display sleep instead, it will connect faster because the system was kept ready to run.
To update these settings, go to your Energy Saver settings in System Preferences on your Mac. What we want to do is let the computer go to Display sleep quickly but set it to go to System sleep later (you still require a password immediately after sleep so the system is secure). This is especially useful when you are plugged in to the power adapter since display sleep takes more energy than system sleep.
As shown above, the computer goes to Display sleep immediately but takes longer to enter System sleep. Please update both Battery and Power Adapter settings to something appropriate.