I have a document with a large number of equations. I have taken a block of equations & moved them. When I select Update Equation Numbers it appears to be doing something but the equations numbers remain the same. This has worked previously. What am I doing wrong?

There are a number of things that may have gone wrong.

If you copy a block of equations that contain an equation section set to a specific value, i.e., "Section 3", when you paste that block inside another equation section, the equations in it would still be numbered (3.1), (3.2), etc.

If you inadvertently changed the field codes to plain text, they would not update.

Equation references cannot be cut and pasted.

Try turning on the Show All [¶]-button on toolbar feature of Word so that you can locate your equation sections, and make sure they are where you want them, and then delete the equation numbers and reinsert them.