I am using Word 2013 and often I use headings (with Styles created for each).

An example of a heading I have is:
1. xxx
1.1 xxx

2. xxx
2.2 xxx

However, often the Level 2 heading (eg 2.2) does not update to match the Level 1 heading selection:

1. xxx
1.1 xxx
1.2 xxx

2. xxx
1.3 xxx (should be 2.1)

I can't figure out how to make this Level 2 heading sync up with the Level 1 heading above it.

Can anyone offer any advice?