solution (of sorts)
It appears that some library parts, are used by Mep Modeler -- with a different icon, as long as I use them
as normal library parts they work fine - If they show a "cabinet" icon then they start looking for a mep modeler key .
ArchiCAD 4.5 --- 27 , Win 10 , dual monitors, 64 gb ram,Nvidia GeforceRTX 2080 TI, I-9