Need advice: Company is forcing me to extend my notice period.

I’m reaching out to share a situation I’m currently facing at work and to seek some advice or support from those who might have experienced something similar. I’ve been working in the cybersecurity field for 8 years, with the last 3 years at my current company. I’m currently serving my notice period, which is set to end on February 11th. However, due to some health complications, I’ve had to work from home for a portion of this period. Despite being unwell, I made every effort to continue working and even came into the office on scheduled days to ensure I fulfilled my responsibilities. Recently, I had a conversation with HR, and I was informed that the days I worked from home due to my illness are being considered as “no work” days. As a result, my relieving date is being extended. I requested that these days be considered as sick leave, but I was told that only critical illnesses qualify for leave during the notice period, and my condition doesn’t meet that criteria. This has put me in a tough spot because my future employer is waiting for my relieving letter to finalize my onboarding. I’m now left with only a few days to resolve this, and I’m struggling to understand how to proceed. Has anyone been in a similar situation? How did you handle it? Any advice or insights would be greatly appreciated.