The "TV Out" connector on the goCoax adapter filters MoCA signals, as it's for a non-MoCA TV. You can't use this output for a Verizon set-top-box. Use a splitter to feed both the goCoax's input and the set-top-box. Leave the goCoax's "TV Out" connector unused.
Make sure you understand the full coax network between the ONT and the various devices. While MoCA can traverse lots of splitters, it doesn't do well with amplifiers or very large numbers of splitters. And remember that an 8-way splitter is really seven 2-way splitters inside a single case. If you've got more splitters than needed, remove some. If there are any amplifiers installed, remove them - they are not needed for fios.
And follow Cang_household's suggests for a step-by-step debugging process.