What are the consequences of exceeding the deadline for a preliminary contract?

A distinction must be made depending on whether the preliminary contract is a unilateral promise to sell or a synallagmatic promise to sell ("compromis").

Does the unilateral promise of sale lapse when the option exercise date arrives?

No. The option exercise date is an extinctive term. The promise therefore lapses. It is imperative to provide for an extension of the promise before the end of the term (art. 1213, Civil Code).
Is the synallagmatic promise null and void if it is not reiterated on the stipulated date?

Most often, the date of reiteration is a suspensive term: it is the date on which each of the parties can summon the other to perform.

When the agreement is subject to conditions precedent, it is necessary to distinguish whether or not the condition(s) precedent (e.g. obtaining a loan) have been fulfilled.

If not, the agreement is automatically null and void on the date set for reiteration (Cass., civ. 3e, March 9, 2017, n° 15-26182).

If the answer is yes, it is advisable to refer to the terms of the compromise. Generally, the clauses of the compromis provide for a date from which the most diligent party may give the other party formal notice to reiterate the authentic act.

In practice, the question arises as to whether the confinement can be analysed as a case of force majeure justifying a temporary suspension of the performance of the contract without either party being able to impute a delay in performance to the other.

Hesitation is allowed, even if one can expect that a court seized of this question will retain the force majeure of article 1218 of the Civil Code if the preliminary contract was drawn up in 2019, therefore before the epidemic was officially noted.

According to this text, it could be considered that this event beyond the control of the debtor, which could not be reasonably foreseen at the time of the conclusion of the contract and whose effects cannot be avoided by appropriate measures, prevents the performance of its obligation by the debtor. According to the Pasteur Institute, the coronavirus was discovered on January 9, 2020.