Lily repeatedly reverts to triangle

My Lily sport edition watch (version 1) was fully functional for the first 2.5 years I had it before it abruptly displayed a triangle and stopped working.  I tried recommended troubleshooting steps, but nothing seemed to get it past the triangle... UNTIL I connected it to Garmin Express on a PC.  Garmin Express recognizes the watch, and after it fully charged, it then briefly displayed normal screens while connected to the PC.  However, it reverts to the triangle within a minute or so when it's disconnected from the PC (and sometimes while it's connected).  It is running software version 12.21.  

Before trying Garmin Connect, I was advised by customer support to exchange it after paying a fee (currently $99).  

Now that it's intermittently functional, is there any further troubleshooting I can do without exchanging it?