For my upcoming BA761, I selected 4A when it bacame available a bit after T-72, as it was the first row of ET. Today, I log into my booking, and see a note that my seat has changed - to 4A

However, clicking on the "view or change seat button" for that flight, gives me no seatmap. It says I'm in 4A, and displays the correct class, but there's no map to chose a seat from.

I checked the flight in Expertflyer, and noticed that row 4 is now the last row of Club Europe - with 4A showing as empty

Expertflyer i showing 9 or more seats for sale in both cabins, so I can't imagine it being an upgrade anyway.