Some headway! In the past and for years my include statement was,

include "DT_INTS-14"
include "ReEnterPBP"

and there has never been a problem until now. So I have changed these statements to,

include "DT_INTS-14.bas"
include "ReEnterPBP.bas"

Now these files seem to open and program compiles.

Got Me! Magic happens!