Company won't able to transact any business unless the number of director increased as per the minimum requirement.
There is no any time limit given but it is understood to do it at the earliest to comply with the requirement of the Act.
The relevant sections are section 149, subsection 1 of section 174, Clause 60 and Clause 69 of Article of Association as per Schedule I of the Companies Act, 2013, Clause 3.4.2 of Secretarial Standard 1.
Remedy - Sub- section 2 of Section 174 of the Companies Act, 2013.
CS Abhishek Anand