Excel: Alert Limit Exceeded

I have a spreadsheet with a small number of cells - 4 tabs. - The biggest circa 860 rows x 30 columns = 25800 cells - The size of the spreadsheet on disk is 225KB. (222,467 bytes) - The cell count in the other 3 sheets are negligible - I think I am under the limits described here ! Hardware: - (MBP 2016) Quad Core Intel i7 - 16GB Memory - Activity Monitor says 7.29GB memory used at the time it happens. OS: - OS Monterey 12.7.3 - **upgrade to OS occurred last night. My gut tells me something here broke Excel.** Excel version: - Excel for Mac 16.81 (24011420) - Licence: Microsoft 365 Subscription I have used far bigger spreadsheets before today with no issue! Any ideas? I have tried: 1. clearing content of rows below, 2. copying data to a new spreadsheet 3. rebooting. All to no avail. The moment I try and enter or paste new data and hit enter in a cell I get this issue. A screenshot is here Others can open and add data with no issues on other hardware - probably Windows users - I shared spreadsheet internally with my colleagues in Teams. I also tried contacting Microsoft Support - but gave up after about 20 min - when I Googled the response time was 2-6 hours! I also ferreted around looking for answers in Excel log files located in this folder - nothing jumped out at me: - /Users/___/Library/Containers/com.microsoft.Excel/Data/Library/Logs/Diagnostics/EXCEL - ___ - substitute your login id for folder name. I also posted here too. Finally: - there was a UiPath forum post that came up in my search - which in turn had an embedded link here . But neither of these made any sense to me.