Error Conversion failed. The transcoder exited due to an error

I’m talking about the " [Error Conversion failed. The transcoder exited due to an error]" message that everyone that uses my server gets (within 15 minutes). It happens to everyone, evey time, on different apps (Roku, AppleTV, LG). Did I post my response to the wrong thread? Sorry, I’m a novice at this. Everything worked for several months and now it is unwatchable. Advice?