Setting AutoFilter via VBA generates error?

This macro was working just fine, now it generates an error on the line in red.

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Run-time error '1004':
AutoFilter method of range class failed

Any hints, tips or examples are welcome.

Is the sheet protected? Is there already an autofilter in place elsewhere?

Your always spot on.
I recall now I had interupted the macro, thus it left the autofilter on. I simply refused to see the autofilter drop down button on that column for some reason.

It always amazes me how the obvious is so easily overlooked.