Hi ssalmon,
What’s the Jetpack version in use?
Are you trying to connect TSC_EDGE_OUT to a GPIO used as PPS input?
You can refer to the following topics to setup PPS first.
PPS input to GPIO on Jetpack 6.1 - #8 by erik93
Pps_gpio interrupt not asserted - #8 by KevinFFF
AGX Xavier PPS fetch timeout R35.2.1(R32.7.1 works fine)