Make error: missing separator

As indicated in the online manual, the most common cause for that error is that lines are indented with spaces when make expects tab characters.

Correct

target: 
\tcmd

where \t is TAB (U+0009)

Wrong

target:
....cmd

where each . represents a SPACE (U+0020).

This is a syntax error in your Makefile. It's quite hard to be more specific than that, without seeing the file itself, or relevant portion(s) thereof.

Just for grins, and in case somebody else runs into a similar error:

I got the infamous "missing separator" error because I had invoked a rule defining a function as

($eval $(call function,args))

rather than

$(eval $(call function,args))

i.e. ($ rather than $(.