What is the proper way to mirror skin weight ? it does not work anymore

It was working in the past but for some reason i cant mirror anymore (cant get it to wotk in 5.4 and also not working in 5.5.1.

Mac m3 max fresh project with 1 imported character

Can you guys tell me the right steps to mirror ear_l weight to ear_r ?
what bone to pick,
what vertices to select,
what plane, - to + or the opposite

Thank you