Until yesterday evening I could switch tabs in an Excel (Office X) page with option-left/right arrow, but, apparently spontaneously, I no longer can.

It doesn't seem to be a pref that I may have inadvertently toggled, but Excel's documentation is pretty convoluted, so I'm not 100% certain.

Has anybody got an idea of what might have happened?

Thanks.

The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire