Letter validity
Officers should understand that the validity date of the letter in no way overrides the authority of paragraph R186(w), which allows foreign nationals who meet the requirements to continue working until a final decision is made on their work permit application.
The letter has a 120-day validity from the date of receipt, which corresponds with IRCC’s service standard for in-Canada applications. Historically, IRCC meets its service standard more than 90% of the time; therefore, only a few applicants will require a new letter. Most should receive a decision before the 120 days have expired.
If the 120 days have passed and no decision has been rendered
In cases where the 120 days have passed and no decision has been rendered, the applicant may request continued proof of authorization to work using the IRCC web form.
Client Support Centre (CSC) agents can follow their standard procedures to respond.
https://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/temporary-residents/study-permits/post-graduation-work-permit-program/permit.html
I applied 16th of November pgwp for me and open work Permit for my wife. Still waiting.