If the supplier is having trouble seeing the documents, it is possible that they do not have access to the documents within the Building, only the documents that were included in the Bid Room, and that no documents were added there.
To fix that, go back to the request for proposal and add the documents you would like the bidder to see.
However, if the issue is happening after the supplier has won the tender process, it is possible they were not granted access to the whole project. Please refer to this article for more information.