The lift needs to be recommissioned to bring it back into service, this would be a reasonable request from you to the landlord. This is the area I would sort first. Surely you rent the building and its facilities, such as a working lift. It will either be broken of require annual certification, both are a cost which the landlord is taking as a saving (and not passing on to you).
OR
As the host of the meeting your company should have made provision for access to the meeting, if this means holding it at another venue then that is also reasonable.
The cost of adjustments is not a good excuse to discriminate against someone, the law sees it that way aswell.