The National Lottery Heritage Fund joined forces with Ipswich Borough Council and Fusion Lifestyle in an attempt to save the lido about eight years ago.
It pledged £3.8m to the project in 2018 and a further £3m in 2023, while the local authority vowed to inject £3.3m.
Permission for the restoration was most recently approved in December 2024 and work was scheduled to start last year, with a view to the pool reopening this year.
But last summer the council said Fusion Lifestyle had been “unable to provide assurances about their financial position”.
The authority said it raised concerns and brought “into question their ability to deliver the project”. The lottery fund then pulled out.