Proposal got rejected with full relationship bars?

Welcome to the fact tht traits don't affect it too much but have some impact.
Lol first you need minimums of 1/2 filled friendship bar and 3/4 filled romance bar
Then put them both in a happy mood, get the conversation flowing till the bar says steamy exchange or something above it.
Then have a sim propose, it doesn't matter which sim does it.
Since you've only tried your male sim, the issue may lie there. Try getting your female sim to propose. Sometimes the issue is with a particular sim. Things become too orquad if they're not kinda good friends or certain 'bad' sims are around. The 'bad' sims I'm talking about are some tht instantly make things too orquad without being active. You don't wanna rush the proposal.