See here: How to Merge Cells in DataGridView | 10Tec
And do yourself two favours:
1) Indent your code! It's a whole load more readable for everybody if you do, and VS will auto indent it to your preferred style for you.
2) Don't swallow exceptions. At the very least, log them to the debug console so you know they have occurred and get some info to help you fix them:
catch (Exception ex)
Swallowing exceptions just means you have no idea what is goin on in your code, or even that it is wrong - like turning up the volume in a car to cover the noise when a wheel falls off doesn't mean that the car is fixed.