We started this process a few days ago with a 28-month-old and a bike with the pedals removed. She was ecstatic to get a bike, and she constantly asks to go outside for bike rides, but she quickly wants off after a few dozen feet.
I think this is normal. It takes practice and requires motivation. You can't force it, but there are things you can do to help. For example, she loves to hold her feet up next to the front hub and get pushed "really fast" (as she describes it). If she asks to go really fast, I'll tell her that I'll push her if she makes it to the corner by herself. As another example, she sees me ride my bike frequently, and I let her "help" me pump up tires and perform small repairs. So she loves the idea of bikes even though bike riding is still a work in progress.
In the end, though, each kid needs to go at their own pace. If it helps, try to think about how challenging and uncomfortable it must be. Keep the bike around as an option, and provide some encouragement, but there's no rush. It's supposed to be fun.