Same issue here!
I started working with the API last week and created my first PAT. What I want to do is fetching the status of my washer every 60s from my local SmartHome system. In the meantime I have created four tokens, each stopped working after 24h.
Here is an example request and response:
--- Request ---
curl -H "Authorization: Bearer <PAT>" https://api.smartthings.com/v1/devices/<Device-ID>/components/main/capabilities/washerOperatingState/status
--- Response ---
<html>
<head><title>401 Authorization Required</title></head>
<body>
<center><h1>401 Authorization Required</h1></center>
<hr><center>openresty</center>
</body>
</html>