Replaced headgasket. Now it turns over. But wont start

Hello, if you have fuel and spark active, and you have air getting in as it should be (or restricted as it should be) and exhaust flow, you should have a functioning engine, if all is as it should be. You could have a timing issue, although you seem certain that you have everything aligned properly. You could have full on air getting into the intake when it could require no air, causing no start. Too hard to say without hands on analysis.