Calc 6.4.6 - Can't figure external references - googling and docs no help

I’m using Calc on a Ubuntu 20.04 system. I’m trying to reference a cell in an external workbook. Opening the workbook and clicking on the “Allow Updating” button results in the error #REF.

The receiving cell contains:

='file:///home/glb/Documents/Business_Financial/Business/2021/business_2021_Budget.ods'#$'January 2021'.J12

The directory structure of /home/glb/Documents/Business_Financial is:

total 19
drwxrwxr-x 2 glb glb 5 Jan 27 16:12 2021

-rwxrwxr-x 1 glb glb  24983 Jan 27 15:38 business_2021_Budget.ods

drwxrwxr-x 2 glb glb     4 Jan 27 15:43 2021

total 45
-rwxrwxr-x 1 glb glb 43659 Jan 27 15:43 Personal_Budget_2021.ods

Clearly I’m doing something wrong. Everything I can find says the above is correct. Does anyone have an idea ?


Duplicate of Having trouble referencing a cell in external workbook (Ubuntu 20)

What is the content of business_2021_Budget.ods#$'January 2021'.J12 - Does your source already contain #REF!?