@gregcan - Most of my rules are very simple and cron initiated. Because many are used to prompt my children on a school day, I use a School Day Switch.
I think your File not found might not be rule related. You can definitely test through the OH Console to verify. All of my mp3 files are in the sounds folder. There are a couple of troubleshooting threads on the site, here is one I tested my configuration, Squeezebox Configuration
I will also add that I have switched to almost all Chromecast Audio players now. The RPi Squeezebox effort was another thing that I had to manage.
Rule example
The following rule is easy to follow, but here are the basics. Using cron, this rule executes at 6:45pm every Sunday through Thursday. The first action is to test if the School Day switch is set to ON. This state is set in another rule that executes every evening to determine if tomorrow is a school day. Next a simple Info log that Bedtime is being Announced. Then the playSound command for the mp3 file. Done.
rule "Bed Time"
when
Time cron "0 45 20 ? * SUN-THU"
then
if (SchoolState.state==ON) {
logInfo("AnnounceLogger","Bedtime")
playSound("Charles_Time4Bed.mp3")
}
end
Has anybody fed the Dog Announcement. Even the dog knows that this is her call to dinner, and you will find her sitting at her bowl in the kitchen. This rule executes every evening at 7:15pm.
rule "Feed Harper"
when
Time cron "0 15 19 ? * *"
then
logInfo("AnnounceLogger","Feed Harper")
playSound("Charles_AnybodyFedHarper.mp3")
end