Repaired head gasket, now it will not start?

Had a blown head gasket, bought Bar's
Leaks head seal  blown head gasket
repair followed instructions
completely. Test drove it and it ran
great.  It sounded good,  no smoke,
no over heating,  nothing that I could
notice. John asset sales actor
repairing this it's real perfectly and
never overheated.
Next morning tried to start the car and
it will not start. It turns over and acts
like it is trying but goes not.
What could be causing this and what
do I need to be doing to fix it ?