8 months and not crawling

My 8 (soon to be 9 ) month old is NOT crawling. When he gets in army position he kicks but he hasn’t gotten scooting down yet. He just doesn’t move then he gets frustrated and cries!! He’s not even pulling. Should I get a Walker this encourage movement?

* he’s been checked out & has no developmental issues. His doctors says he say “first baby/only child” syndrome. He’s just moving at his own past because he’s not around any kids and being the only child he’s always picked up.