The best OP is going to do is to receive a refund for the original tickets via a CC dispute. But, even that will be heard as the opaque third-party ticket vendor will simply assert that it properly ticketed the passengers and that whatever it is that went wrong, went wrong as the result of somebody else's screw up.

OP won't recover the cost of the new tickets because a CC dispute won't help there.

OP is left suing the third-party vendor and that may well be -- depending on jurisdiction -- well above small claims limits.

This, unfortunately, was all avoidable. It took about 30 seconds to locate numerous websites with consumer complaints against this outfit. Any time you see any appreciable number of complaints, even if there are some satisfied customers out there, do like Nancy Reagan and "just say no."

In terms of what unfolded, as soon as OP no showed on the connection, the remainder of his ticket was cancelled. That happens with pretty much all carriers and their tickets. So, the sole question here is why the segment in question was cancelled.

Having dealt with that one segment, unfortunately it was on OP to make certain that the remainder of his ticket was still intact or reinstated.

Not sure that travel insurance would have helped here.