It seems that it wraps around rather than returning an error.
https://go.dev/play/p/s2aA3-ERd-E
Uses timestamp 2000-01-01T00:00:00.00Z and zeros for the payload.
Returns: WfeXVK2UN8Qh86bSI6R4zNvC7ge
$ ksuid -f inspect WfeXVK2UN8Qh86bSI6R4zNvC7ge
REPRESENTATION:
String: WfeXVK2UN8Qh86bSI6R4zNvC7ge
Raw: E4FAF58000000000000000000000000000000000
COMPONENTS:
Time: 2136-02-07 01:28:16 -0500 EST
Timestamp: 3841652096
Payload: 00000000000000000000000000000000