Last Update: 1/8/2019
Origin 2017 introduced "Spreadsheet Cell Notation" (SCN) for use in column-based calculations in the Set (Column) Values dialog box. Origin 2018 extended use of spreadsheet-like notations to cell formulas (cell-level calculations).
Occasionally, users disable all or part of the cell formula functionality, either via the GUI or LabTalk command and forget that they have done so. Later, they attempt to make use of the cell formulas, then find that they do not work.
Note that there are LabTalk (script) methods for disabling spreadsheet cell notation for a single book and for disabling it for every existing book in the project, including new books. These are covered in FAQ-849 Can I turn off or selectively control use of spreadsheet cell notation in my workbooks?
There are several ways to partially or totally disable cell formulas in the Origin project (see FAQ-939 for details).
Make sure that Edit Mode is not simply enabled:

Make sure that LabTalk System Variable @ESC = 1. If @ESC=0, cell formulas (e.g. "=A1+B1") will be treated as simple text and expressions will not resolve. This will happen even if the workbook window's Spreadsheet Cell Notation box is checked and Origin's Edit Mode is turned off.
@esc=
@esc=1
Also, if @ESC returns a value of 0, check the Set System Variables dialog to see if you have an "ESC" entry that is set to 0:
Keywords:calculation, spreadsheet, @RCN, @ESC, page.xlcolname, ClrX