Developer key works with spromeps.lib 5.39 but not 7.1.0

We have been using spromeps.lib 5.39 with SentinelProtectionInstaller_7.4.0.exe for a long time without problems, but now we need to build a 64 bit version of our product. I found a version 7.1.0 spromeps.lib that has both a 32 and a 64 bit version. If we use the same source code and link against either the 32 or 64 bit 7.1.0 spromeps.lib, we get SP_UNIT_NOT_FOUND when calling RNBOsproFindFirstUnit(&sproHandle, key), whereas linking against the 5.39 version we get SP_SUCCESS.

Should the same developer key work with versions 5.39 and 7.1.0 of spromeps.lib?

Thanks for any help.