Will a Larger Pipe Make Our Sprinkler Work?

It may improve it but not solve the problem.

You should find the problem. Was there new development above or below you?

The municipal mains are usually ring mains (that is the water may reach you from more than one direction). if some of the isolating valves are closed the water may have to take a longer route to reach you and lose pressure.

"One bar at source" (15psi) sounds horribly low for a water supply pressure. You could normally expect around 60-100psi as a supply pressure and if this is the pressure at the supply point but the sprinkler is not "sprinkling" one possibility is a build-up of debris (rusting pipe matter, dissolved soil from repair exercises) clogging up the sprinkler holes.

Bigger pipes won't help. You need more pressure. Or you have a restriction. If 3/4 worked before.........................................

One bar at source is very low. I suggest you check to see if your pipe is leaking or clogged first. A leaking pipe should be easy to locate: look for spots where the grass is greener and growing more lushly than others, or where the ground is inexplicably soggy.

Get a big water pump.