Sudden "Type mismatch error"

Hi all

I've had a macro running on a shared spreadsheet for a few weeks now with no issues, but this morning it has decided to stop working and give me the "Run-time error '13': Type mismatch". I don't have much experience with macros and most of this macro was written by someone else so I don't know exactly what I'm doing.

I've only attached the sheet with the macro in it as the rest of the spreadsheet contains confidential data...

Here's what the macro is meant to do:

Every time a cell in column A updates (based on a gigantic nested IF formula) then
update column O with the value of column B
update column C with the value of column A
update column B with the current date

Debugging the macro shows it gets stuck at

Formula:

If rngC.Value <> rngC.Offset(0, 2) Then

I hope this makes sense, thanks