The Ryobi has now decided that it doesn't want to start at all from
cold. A case of removing the plug and giving a shot of easy start.
It then goes at third pull. I'm not sure the primer bulb is working
properly, but it has never been a good starter.

Try a gas blowlamp. Don't light it, just play unlit gas into the air filter
whilst starting. Most small engines start easily on a whiff of gas providing
the ignition spark is working reasonably well.

Mike