You are justified in issueing a Show Cause. Usually support payments are late after 30 days (at least that’s how it is when you use Child Support Enforcement).
With men like your ex, the BEST thing to do is to have the child support ordered throught Child Support Enforcement. This is how I have mine done. From what I was told, if he gets in arrears, the Agency issues a Show Cause on your behalf. They have records of his SSN and such. Men like your ex (and mine) can’t be relied upon to make right on the order unless you MAKE him do it. That means issueing Show Causes when he gets behind. Yes, it will take time to do that. But he will have to show up to court with PROOF that he has paid you (and he could pay you the morning of court). If he has no proof, then he can get in big trouble. My ex was going to be given jail time, but we worked it out with the court. But it woke him up to his responsibilities and I’ve never had another problem with it.
I would proceed with the Show Cause. You are justified…especially after 30 days late.