ELI5: Threat from maturing CMBS for major metros?

https://www.bizjournals.com/washington/news/2023/08/17/cmbs-loans-commercial-real-estate-washington-dc.html
 

 Looking for a little guidance on how to best understand the story being told here regarding CMBS default for office sector properties impacting major metros.
 

This is my understanding of the story. Would like some confirmation that I am understanding this correctly:
 

This article describes an environment where office owners are missing monthly mortgage payments more consistently (due to vacancy rates) and the typical exit path of refinancing or selling are not attractive due to high refinancing rates and weak demand from buyers for a struggling asset class (compounded by high borrowing rates)?
 

What does it mean when a loan approaches maturity?
"Normally, when their loans approach maturity, office owners would simply refinance, or perhaps sell." Why would someone refinance if their loan is approaching maturity when the final payment will be made and the loan will be closed? Why would you wait until the loan matures to refinance instead of refinancing earlier during the life of the loan?
 

Thanks