DerbyDad03 wrote:
What could cause this:

GFCI on a supposedly grounded circuit. Wires appear to be installed
correctly at the GFCI.

3 light tester shows Open Ground.
115V between hot and neutral
54V between hot and ground lug
46V between neutral and ground lug

Thoughts?
Hmmm,
Are you using DVM? No analog meter?
GND is missing.