Low or no oil pressure on new engine, wtf now...

You did right by removing the sender to verify oil flow. And right again about not running it. As a rule, I've always taken the new pumps apart to make sure they are clean and make sure the relief valve works. You may have one stuck open. As long as the tnesioner was installed properly they won't affect the oil pressure. With that HV pump you should have a ton more pressure. Also, when the pump was changed... was the pickup to oil pan clearance verified?