We are using an LMS called Traccess CI. I've created a fairly simple 15-question test, and set the rules to pass/complete if all questions answered correctly and to fail/incomplete if any questions missed.

The test loads successfully to the LMS, but once completed, the scores will not transfer. We've looked at the load of this Courselab test vs. some scorm 1.2 content from other providers and the settings on the LMS side are consistent. We've decided it must be something in the courselab test that is not transfering the scores. Any ideas?

You don't say which courselab version you are using, however the SCORM API is standard, that is it is the same as any others content using the same standards.
It may be more a case of what Traccess is collecting, it does cite compliance up to scorm 2004 but doesn't detail this.
The web site for this LMS is pretty sparse and there is practically no useful information there.
The available online help is not exactly helpful either as there are no technical details of the system, it is just a quite simple user manual.

Have you tried the same content published as 2004?

As this is a commercial purchase you should be able to ask the developers there. It may well be something really trivial in the transfer process itself like the variable name used for the score transfer. Something as small as the difference between total and Total can make this fall over.