The contract is designed and build but the approved design will be changed by the Client. We submitted a proposal but the Client is not issuing any approval nor comments. We are about to finish the available works in a couple of months and yet no words from the Client. Are they in default? How can we prove the Client is in default? Contract is FIDIC 1999 EPC Contract.
I do not know the contract form which you referenced, but most design-build contracts have clauses under which the owners represents that their timely approvals will not be unreasonably withheld. If you wamted to reach out, I woudl be glad to take a look at the contract and give you a more informed opinion.