The build is part way up, the contingency is gone, and the remaining draws will not cover what is left to do. Lenders call this a cost to complete shortfall. How it gets solved, and what it costs you, depends almost entirely on how early you put your hand up.

A construction lender is not tracking what you have spent. It is tracking what it will cost to finish. The quantity surveyor reports on work in place and on cost to complete, and advances are made against work in place.
If the remaining commitment will not finish the building, draws stop, regardless of how much has already gone in. The construction draws guide sets out how that process runs when it is working normally.
A shortfall identified at forty percent complete has options, including rescoping, value engineering and a modest equity top up. The same shortfall found at eighty five percent with trades unpaid and liens going on title has very few.
Lenders would far rather hear about it early, and their willingness to help drops sharply once they feel they were not told.
More sponsor equity. The cheapest route and the most common one.
An increase from the existing lender. Possible where there is room in the loan to cost and the completed value supports it. How that facility is structured is covered on the construction financing page.
A mezzanine or second position loan. Behind the construction facility, expensive, and usually needing the first lender's consent.
A full refinance. Replacing the construction loan with a lender who will fund the larger budget. One thing to be plain about: the statutory holdback is not available for any of this.
Paying trades outside the draw schedule. Understating the remaining cost to the quantity surveyor. Letting liens be filed.
Each of those narrows the options that are left, and none of them buys any real time. If the project has already stopped, the stalled project page covers what happens next.
Send the quantity surveyor report and the revised budget. We will tell you what closing the gap realistically looks like.