'in Excel 2016, in my worksheet there is a block of cells (rows & columns) that will not accept a "fill" instruction. The rest of the sheet above and below do just fine. Any advice would be appreciated.'
To give you a quicker solution and to understand it better, please explain it in more detail and if possible add a file (without sensitive data). So some could offer you a solution more quickly.
It could be something that is causing this, for example a macro or that these cells could be locked in some way, etc.
I know I don't know anything (Socrates)