ConstantContact hasn't got back to me yet so I'll post here for the next person getting these issues. Since my first account seems to be broken because I asked for Partner access, I created a new account. I was VERY careful to get the correct URL because CC seems to have issues caching/updating them. This worked fine for my development/test env (although it kept asking me to log in and grant acccess EVERY time, which I guess could just be an annoying "feature"). Once I was happy with that, I created another app under my new account for my production site. This has caused the old "the client ID : [my new app id] is not valid or has been disabled" to happen again. I'm going to create a new-new account for production now. Wish me luck.
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