Although most of the major Android OEMs have already rolled out Android 9 Pie to both pre-existing and new devices, HTC only started over the last week or so. The first device from the company to see Pie was the HTC U11 from 2017.
Unfortunately, some U11 devices in Taiwan that received the update face a huge issue: the stored PIN and pattern security codes don’t work (via XDA Developers). This effectively bricks the device as there isn’t a way for the user to unlock the phone.
In response, HTC halted the rollout of Pie to all U11 devices. The company is also offering free service to anyone who upgraded and can no longer use their phone.
As of right now, it appears the Pie upgrade only shipped to Taiwanese handsets. If this problem affected your HTC U11, visit this page to get the service you need to fix the issue.
If you didn’t update yet, you’re in the clear, and a new update will start rolling out tomorrow, June 6. Assuming that update doesn’t face any issues, the update will fan out to other countries outside of Taiwan soon after.