that pvc to corrugated is a mess and a unreliable nightmare.
It is just not sound engineering. If your yard slopes off enough I would trench in sch 40 pvc to all the down spouts
and network them down the hill and let them run off, This way you have no underground leaks. and a reliable system. You can see what I do at garrettplumbingco.com
If the contractor will not call back tell him you will
file a law suit for fraud, That almost always gets a return call. "nice" doesent work with some people.
Good luck

Interesting. Thanks for the response. I dug up all of the pvc-corrugated pipe connections. Only one had not been duct-taped together. I taped that one up and punched a couple of holes in the currugated pipes near their connections to the pvc pipe to prevent standing water from collecting in the near the pop-up. I was also able to find a piece of pvc that allowed me to raised the height of the pop-up thingie by 3". This allowed me to drop the corrugated pipe 3" deepter near its connection to the pvc pop-up pipe.

Hopefully, this will solve my problems.

So I would have been better off using pvc instead of corrugated pipe.... Thanks for the info. Sure wish I had known before it was installed. Oh well....

Of course, a taped joint is not likely to be watertight. You might try Pasco 10-mil pipe wrap tape instead of duct tape. It can be used underground and will adhere tightly even when wet.