If the original Bank Guarantee has expired, and your appt. is still not finished, it is possible it has expired because the development is delayed.
Insist that your lawyer obtains a new Bank Guarantee (he should be doing this anyway if he’s any good, you shouldn’t have to ask….) – but make sure the enforcement date is not too far in the future.
There must be a date when completion is supposed to happen (in your contract…?).