Is it obligatory to boycott a brother in faith who appears committed and accepts advice without acting upon it, and repeatedly commits forbidden acts such as listening to music and speaking with non-mahram female relatives online?

One who commits a sin openly should be shunned if shunning deters them or reduces their sin. As for one who commits a sin secretly, they should be advised privately, and their sin kept hidden. Shunning is permissible if it affects the shunned person and does not lead to a greater evil. Shunning varies depending on those who shun. If the benefit of rebuking and disciplining the shunned person outweighs other considerations, then it is lawful. However, if it increases evil, then shunning is not prescribed.