The Home Office will refuse or stop your section 4 support if it says you are able to leave the UK. Your Home Office decision letter may say 'there is no legal or practical obstacle' to you leaving the UK.
To get section 4 support you must be:
Reasons which might mean you are not able to leave the UK include: fresh claim/further submissions, judicial review and medical condition.
If you have a lawyer, ask them to write a letter which explains this information.