Bruce T
I agree that you dont want to work on this yourself!
But an (honest) plumber will use a multimeter (with the power off orf course) and check for continuity by touching the leads to both posts of the element(s) to see if the element has burst, and also he can touch the metal tank and one of the posts to see if it has grounded out to the tank.
if both elements are good, the high limit of one of the thermostats could have “thrown”..wich usually meens a bad thermostat.
all in all, if this thing is over 9 years…It may be cheaper to get a new one and have it serviced regularly! (flushed and anode rod inspected) especially in hard water inviroments.
