You select a cell, and then from menu Freeze Panes!

All rows what are above selected cell are freezed;
And all columns what are left at selected cell are freezed!

Obviously you selected A5 instead of B5!

And be sure you have scrolled the page to start (at top and at left), otherwise can happen, that you don't see some freezed columns/rows anymore unless you unfreeze page!

Another issue newbies sometime have is, that they scroll the sheet to start, but forget to select the cell, leaving the cursor active somewhere near AA100. And then can't understand, how they can't to scroll the page at all :-)