I'm trying to connect some dots here because you've left out a lot of details. What exactly do you mean by "get precheck?" Do you have a KTN from TSA? And usually your boarding passes show TSA PRE on them? But not on your last flight?

What makes you say that you there was an issue with the mismatch in names? In my experience, on the rare occasion that my boarding pass (with any airline) doesn't show precheck, I have not been given a reason aside from being reminded that it is not guaranteed.

Or was your last flight your only flight on UA since getting the KTN? Did the web site or app tell you there was a mismatch in names? If so it may be something that a human at UA could resolve.