I work for a software company. A company hired us to patch some functionality on an existing system.
After a few meetings, we agreed that we would need information about the current system, as well as data (from a database) that would allow us to write the new functionality.
Time passed and we constantly received incorrect information from the client. The deadline passed and we spoke to the client, who asked us to be patient as they would have to speak to their DB service provider and gaining data. After a while, they gave us some data that was broken and incomplete.
We don't want to drop the project, but their deadline for the functionality to be used is rapidly approaching. How can I let the company know, professionally, that we cannot complete the project due to the missing and broken information that we received from them?
They are an existing client that we have successfully built systems for, and we wouldn't want this to affect our working relationship.
What can I do?