IPs should always beware encouraging clients to make offers of equity release on shared ownership properties, because as Catallus has already highlighted this is nigh impossible. You may be able to get a secured loan, however, which is not an ideal solution but could enable you to comply with the IVA terms.
I suggest that you now discuss this matter with your IP directly, and ask them to explain why this was not considered at the time the proposal was formulated.
If you are unable to raise any funds at all, it is unlikely that your IVA will fail - perhaps your IP could put forward a variation enabling you to make additional contributions in lieu of the equity, given the circumstances.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk