What's more concerning is the fact she did not receive 48 months extension letter. In 2023 USCIS sent out 48 months extensions to everybody who had pending I-751. This would have extended her GC for another 2 years.
The reasons why it's concerning is if you never received new extension letter, you might as well missed interview appointment letter, RFE, NOID or denial.
Did you move since filing I-751? If moved, did your wife file AR-11? Did you file I-865 if you moved?
You can request missing notice (48 months extension) here https://egov.uscis.gov/e-request/displayNDNForm.do?sroPageType=ndn&entryPoint=init