Trouble with napping

Yesenia

Is anyone else having a hard time getting their baby to nap flat on their back? My son will only sleep flat on his back at night in his bassinet but won’t nap on his back during the day - he’ll only take naps in his vibrating bouncer that came with the pack-n-play. I’ve tried putting him in the actual flat part of the pack-n-play when I see he’s tired but he’ll just cry until I pick him up and put him in the bouncer. Any tips or advice?