As others said – bubs will crawl in their own time. I’d put toys in front of mine so they’d be interested. But eventually they all crawl in their own time.

Are his arms and legs strong enough to support him yet?? He may never crawl properly. One of ours mainly slid along with one hand on the floor on his btm, carrying the toy he wanted in his other hand. He did crawl properly sometimes.

putting some toys that are just out of reach. they will soon begin to crawl in their own time.

Lots of tummy time! Sit yourself or a favourite toy in front of them, so it can be seen, to encourage them. Bub won’t do it til he’s ready though, regardless of what you do

Place some favourite toys close by but juuust out of reach to encourage forward movement.
As other posters said- he will get there! Just let him go at his own pace

let him roll a ball and try to get it again

How old is your bub and is there any reason why he needs to learn quickly? He will do it at his own pace babies are funny sometimes they can just pick things up almost overnight, good luck

Only thing I can think of is put something in front of him that he would really like to have and maybe he might want to crawl towards it.