AVR ATtiny1634 - Programming Issue
You are not using an external "Crystal Oscillator", you have an external crystal.

An external oscillator is an active device that produces a signal by itself, a crystal (or a resonator) is a passive component that is a resonant element to control the frequency of the oscillator internal to the AVR.

This is a fairly common error that people make that is not helped by the nomenclature Atmel/Microchip uses.

The solution to "unbrick" the device is to provide an external clock to the controller X1 pin to allow the fuses to be reprogrammed with the correct value.

There are many ways to provide the clock and even an Arduino can do it as a wide range of clock speeds are acceptable provided it is at least 4x the speed at which the programmer operates.

Here are a couple of links to help you on your way:

Recovering a bricked AVR
Unbrick bricked AVRs