Final answer:
Romeo did not receive the letter from Friar Lawrence because the messenger was quarantined due to a plague outbreak, and the letter contained crucial information about Juliet's feigned death to avert the tragedy.
Step-by-step explanation:
In William Shakespeare's tragedy Romeo and Juliet, Romeo did not receive the letter from Friar Lawrence because the messenger, Friar John, was unable to deliver it. Friar John was quarantined due to an outbreak of plague and thus, prevented from leaving the city.
The importance of the letter was that it contained information about Juliet's fake death—a critical detail intended to prevent the tragic ending, informing Romeo that Juliet's death was a ruse and that he should wait for her to awaken from the effects of a sleeping potion.