

Also, maybe the receiver connecting the computer and the wireless keyboard is spoilt hence limiting the connection. One reason the wireless keyboard cannot work is that it may be that you have not plugged in the keyboard well to the receiver. But the good thing is that you can solve these issues in minutes. In addition, Windows may often fail to detect the keyboard, implying that some things cause this failure. I suspect that when you turn FileVault back on again, that 3rd party driver for your devices moves to the unencrypted part of the SSD and is accessible before the login screen and then the Mac can connect to your devices on startup.After setting up your windows, or maybe you have just made an update on it, the wireless keyboard may fail to work. When you turn off FileVault, then everything on the SSD drive is accessible prior to login, including the drivers for the 3rd party Bluetooth devices.

It’s also probably why native Apple bluetooth devices will always connect on startup - because those drivers are stored on the same part of the SSD that houses the MacOS. That means that the drivers for your device won’t get accessed until AFTER you log in, which is probably why it won’t connect to your 3rd party bluetooth device until after connection.

When you turn on FileVault, everything you do after that takes place on the encrypted part of the SSD. I suspect that you connected the 3rd party Bluetooth devices after you turned on FileVault on initial setup. Now the next question is “why”? here is my theory:

And then when you turn FileVault back on, it will connect on startup as well. Bottom line is that you need to turn off FileVault, then reboot and your devices will connect on startup. I had this issue too and spent about an hour with Apple tech support and figured out how to fix this problem.
