Advice on next steps career

SonI resigned from my current org based on an offer from another company. The new org asked me to buyout my notice period and gave me a offer to join on last week of Jan stating they will give me a new offer letter for 5th Jan. Now they are delaying my onboarding till last week of Jan. My issue is that if they would’ve told me earlier I would’ve served my notice got my salary and payout bonus but now I am not getting anything. What to do?