Hi mpgmike!
Thanks for your reply. This is what is written in the notes area of the code in question. I didn't write this code as I'm only trying to update it.
"'PIC is PIC18F66J11
'Using PBP3 GOLD 3.1.3.4
'MPASMX V 3.30
'Microcode Studio Plus 5.0.0.5 / `1'Microcode Studio 5.0.0.5"

This relates to the environment in which this code was developed back in June of 2018.
I assumed this info to be correct but now that I use the newer version below, it fails.
"'PIC is PIC18F66J11
'Using PBP3 GOLD 3.1.3.4
'MPASMX V 5.50
'Microcode Studio Plus 5.0.0.5 / `1'Microcode Studio 5.0.0.5"

I just didn't understand why the code compiles with the COFF check box unchecked and not with it checked.
I have other code that has it checked and it makes not different whether it's checked or not.

I did go back and set MPASMX V3.30 as the assembler but still not success.
All this started when the code was recompiled with the new environment and then it didn't work anymore.
I can rewrite the code, that's not an issue, I just wondered what the problem was.

No need to make anymore posts, thanks for your time.