Welcome. I am Mike, an experienced field technician. We are now connected together on this convenient website where I am able to help you.
99% of the time when the tv won't come on and the LED is flashing it means there is internal hardware failure that requires parts and service. You could try unplugging the power cord and holding the power button for 30 seconds then plug the power cord back in, but this does not cure hardware failure.
The back panel needs to come off, complex checks need to be performed with a meter, then parts ordered and installed. If that is something you want to attempt then reply back here and I can assist you further.
If you are unable or unwilling to perform any of these procedures then a repair shop should be consulted but I can tell you that diagnosis, parts, and labor will end up costing almost as much as a new 50" Tv and could take a few weeks to get all sorted.
I do understand that finding out your tv needs expensive repairs is not pleasant but please keep in mind why you came here to use this service.
An in home diagnosis by a local repair shop costs $100-$135 up front. Finding out whether your tv can be repaired and how much it may cost from this online chat costs a fraction of that!
Before you go please take a moment to submit at least a 3 star rating at the top of this page so that I get credit for my work.