Excel's WorksheetFunction.IsError stopped working when Excel is automated by C#

dean kinnear 1 Reputation point

As of some time this week or last,
Application.WorksheetFunction.IsError no longer works.

All cell errors return false.
e.g. app.WorksheetFunction.IsError(cell.value) is false when the cell formula is =1/0

Also, I am getting: Exception from HRESULT: 0x800A03EC when using get_Range method in non-US locales

Worksheet.get_Range("F7,F8,F9,F10,F11,F12,F13") works fine when using US locale.
When I switch to es-es locale, the 0x800A03EC error is thrown
This stopped working about a month ago.

Neither of these issues happen when using VBA

Microsoft® Excel® for Microsoft 365 MSO (Version 2204 Build 16.0.15128.20278) 64-bit

Office Development
Office Development
Office: A suite of Microsoft productivity software that supports common business tasks, including word processing, email, presentations, and data management and analysis.Development: The process of researching, productizing, and refining new or existing technologies.
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