How to sum from multiple worksheets by matching unique codes

Sorry for off-topic interjection:

Although there is no official rule regarding this behavior, we request that wherever possible both the question AND the answer be provided in substantive detail here within the thread. An attached workbook is an excellent aid for posing a question and offering a solution, but solely doing that with no in thread explanation makes it difficult for researchers to understand or consider the Q & A of this thread without downloading what may be a pointless doc to them, if they can do that at all. Doing that also hides the content from search engines so others may never benefit from this.

I'm sure you understand, and we look forward to seeing you post your formulas/macros in your posts for the searching benefit of all.

Thanks again for all your hard work here!

Note that the name for sheet RT2 has a leading space that the other sheets dont have

hmm OK, fix that and it looks like your formulas work now

Here is a shorter way to do what you wanted.
1. Create a list of all your sheet names
2. Give that list a range name (I used Sheets
3. Use this...
=SUMPRODUCT(SUMIF(INDIRECT("'"&Sheets&"'!A2:A40"),A2,INDIRECT("'"&Sheets&"'!C2:C40")))

Because your formula is not using column B as the search criteria, not column A

Happy to help