Thanks Kaz and Salavator
Per your advice I removed the trunk liner and examined the power cable to the amplifier. The wires looked ok and it was correctly plugged into the amplifier socket. However, there was a small plastic lever at the socket connection that was a bit loose. I pressed the lever down to its locked position which more fully engaged the plug. Now everything is working correctly (wow - going 1 day without audio was painful!)
Removing and reinstalling the trunk liner was a bit of a pain and I worried about breaking the plastic rivets, but it it all worked out fine in the end. The CD install instructions on BWM325i.net (very well illustrated with photos) were helpful.
Sallvator, I appreciate your safety comments about transporting propane. In my case I thought I had it secured using my BMW accessory “cargo net”. However, the net was too small to place over the upright tank, so instead I placed it around the tank, “pinning” it against the trunk opening. This seemed secure, but the tank slid out when I cornered and the rest is history. Next time, I’ll place the propane tank on its side, and use the cargo net on top.
Thanks again everyone