I've been using my on5 since Christmas, and I've only ever had issues with storage (but that got fixed). I installed an app called Next for a new lock screen, and my phone started not registering touch screen interaction the morning after. I've tried accessing the turn off/restart/emergency mode, but when I do so it pulls up the page for my PIN. I tried force restarting, but all it did was vibrate.
Do I need to get my phone connected to a computer and manually remove the app?
Yikes! It sounds like this lock screen app is working a little too well. Are you still having trouble with this? I've never used the app myself, and our third party app troubleshooting options are limited since we are only trained on native applications - but the good news is that you chose an app that at least has a reputable manufacturer: Microsoft Garage. I did a quick search online and they actually seem to have their own user forum here: Next Lock Screen Forum. It looks like you're able to reach out to them in the upper right corner of that page, perhaps they can point you in the direction for how to fix this or uninstall, if you're still stuck?
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