Is there such a clause, and can the Government reject the Deliverable since the 30 day review period has lapsed?
It all depends on the contract. The FAR contains multiple inspection clauses, however only one of them contains a presumption of acceptance. FAR 52.246-6 Inspection - Time and Material and Labor Hour, subparagh (e) states:
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"(e) Unless otherwise specified in the contract, the Government shall accept or reject services and materials at the place of delivery as promptly as practicable after delivery, and they shall be presumed accepted 60 days after the date of delivery, unless accepted earlier."
So you need to check to see if this clause is in your contract and if it is - validate the timing of receipt of the deliverable against the Government response. You will also need to see if any other section of the contract (specifically E, F or G) contains any unique or specific language as allowed by the clause that changes this presumption. If there is supplement instructions you'll need to evaluate its impact and/or address it to the contractor. Recommend you consult with your program attorney after review the terms and conditions of the contract for final resolution.