Hi group

I have 91 EX accord Automatic tranny ,car for over a year.
There has been no problem with this car except once I had to change the main
relay, which we know is a common problem in Hondas.
Today my car was working fine till the afternoon and I parked it and when
came back after 10 mins or so, it wont start. I think the battery is fine, I
am not able to figure out the problem. Could be the main relay again ?

BTW, today I gone to get smog check done, the car passed the test. Could
there have been anything gone wrong after the test that could have caused
the car to be dead.?

Please help.
TIA
HNB.